"The violence that’s taking place there is facilitated in large part because of Russian support," Obama said. "If Mr Putin makes a decision that we are not going to allow heavy armaments and the flow of fighters into Ukraine across the Ukrainian-Russian border, then it will stop.

"He has the most control over that situation... and so far, at least, he has not exercised it."

Watch: Obama: Putin must push separatists to aid MH17 probe

Russian president Vladimir Putin, who has denied Russian involvement in the fighting in Ukraine, said the government in Kiev bore responsibility because the crash wouldn’t have occurred without the current strife with separatists battling regular forces in two eastern regions of the country.

Speaking at an appearance with church leaders near Moscow, Putin called for an end to fighting. “Direct contacts between all conflicting sides should be immediately established, all sides in the conflict must immediately stop military actions and start peace negotiations,” he said.

"It is with great concern and sadness that we are watching what is happening in eastern Ukraine. It’s awful, it’s a tragedy."

The comments came as the Ukrainian government and pro-Russian rebels agreed to set up a security zone around the crash site, Ukraine’s security service chief said on Saturday.

Internationally mediated talks “concluded with an agreement to set up a 20-kilometre security zone so that Ukraine could fulfil the most important thing – identify the bodies [and] hand them over to relatives,”Ukrainian Security Service head Valentyn Nalyvaychenko said in televised remarks.

The UN Security Council unanimously demanded a “full, thorough and independent investigation” at the start of a meeting on the Ukraine crisis that saw fraught exchanges between Western countries and Russia.

“This war can be ended,” US Ambassador to the UN Samantha Power told the council. “Russia can end this war and Russia must end this war.”

As moves to investigate the crash got under way, Ukraine’s state security service said it intercepted phone conversations among pro-Russian militants discussing a missile strike that knocked Flight MH17 from Amsterdam to Kuala Lumpur out of the sky 50 kilometres from the Russian border yesterday.

Ukrainian emergency services have found the plane’s black boxes at the crash site, Kostyantyn Batozsky, an adviser to the head of the Donetsk regional administration appointed by President Petro Poroshenko, told reporters, though he was unable to give details of their current location. The government and rebels are discussing the creation of a safe corridor to the crash site and a demilitarised zone around it, he said.

The aircraft, en route to Kuala Lumpur from Amsterdam, crashed over Ukraine on Thursday after a presumed ground-to-air missile attack.

Ukraine Foreign Ministry representative Andriy Sybiga said 181 bodies had been found from the airliner, citing local emergency workers. He said the bodies will be taken to Kharkiv, a government-controlled city 270 kilometers (170 miles) to the north, for identification.

The identities of twenty passengers on the ill-fated Malaysia Airlines flight MH17 have yet to be verified, Malaysia's transport Minister Liow Tiong Lai said at a press briefing in Kuala Lumpur, adding that the airline is still trying to contact the relatives of those passengers.

At least one Hong Kong resident and a relative with foreign nationality were on board MH17, the Hong Kong Immigration Department said on Friday. The Hongkonger on board MH17 is understood to be a 50-year-old man. The relative with him was his wife, also aged around 50, who held a Malaysian passport.

Malaysia Airlines confirmed on Friday afternoon that 173 Dutch, 44 Malaysians, 27 Australians, 12 Indonesians, nine Britons, four Germans, four Belgians, three Filipinos, one Canadian and one New Zealander were on board the jet.

READ MORE: Hong Kong resident was on board flight MH17

"Chinese nationals are not on the list that they have," a spokesperson told the South China Morning Post.

The spokesperson said the airline wanted to avoid earlier mistakes in revealing unverified identities too soon. Of the 183 passengers, 41 transited in Amsterdam without passing passport controls there. 

Spokesman Qin Gang said on Friday afternoon China conveyed profound condolences to the victims and will closely follow the development of the incident.

"We are deeply shocked by the crash of MH17... We hope to find out the cause [of the incident]," said Qin.

"All of China's relevant embassies and consulates have activated the emergency system to confirm if there were Chinese citizens on board. We will closely follow the development of the incident, keep in close contact with all parties involved, and take actions in accordance [with the development of the incident]."

Ukraine has called for an international probe to determine who attacked the plane and the Unites States has offered to help. But access to the site remained difficult and dangerous. The road from Donetsk, the largest city in the region, to the crash site was marked by five rebel checkpoints Friday, with document checks at each.

The Organisation for Security and Co-operation in Europe (OSCE), a multinational grouping that has played an observer role in Ukraine's conflict, sent staff via helicopter to the rebel-controlled area where the plane's wreckage lies shattered, a spokesperson for the organisation told the South China Morning Post.  

Prior to their departure, the OSCE held talks with the militants who have agreed to their presence.

"Today 17 new workers and four official experts from Kiev arrived in Donetsk," said rebel leader Sergei Kavtaradze. "Soon they are due to arrive at the site of the tragedy. We support the maximum number of experts possible."

The OSCE later said about 30 of its staff had arrived at the scene.

Watch: Downed Malaysia Airlines jet MH17 - what we know so far 

The Ukrainian government and pro-Russian separatists are meanwhile continuing to trade accusations over who shot down the Malaysian airliner. Both have denied taking the plane down.

Ukrainian Prime Minister Arseniy Yatsenyuk described the downing as an “international crime” whose perpetrators would have to be punished in an international tribunal.

“Yesterday’s terrible tragedy will change our lives. The Russians have done it now,” he was cited as saying by the Interfax-Ukraine news agency.

Suspicion has fallen on pro-Moscow rebels in the divided eastern Ukraine, branded “terrorists” by the government in Kiev, who are in control of large areas of the region.

INFOGRAPHIC: Shot down over Ukraine

According to intercepted audio recordings from conversations between rebels shared by the New York Times, the jet just “fell apart in the air”.

In one phone call, pro-Russia separatist rebel commander Igor Bezler allegedly informed a Russian military intelligence official they had “just shot down a plane,” according to the recordings.

Bezler allegedly ordered his men to intercept the pilots of the stricken “smoking” jet.

One of the men concluded the plane was a civilian aircraft after stumbling across the remnants of internal brackets, seats and other “civilian items”, according to the recordings. The militants described seeing “lots of corpses of women and children”.

In the confusion one of the men said he had learnt from a television report that the downed jet was an AN-26 Ukrainian transport plane, but went on to say “but it has Malaysia Airlines logo on it.” He went on to question why it was flying in Ukrainian airspace.

The caller on the other end of the line concluded the plane was carrying spies. "They shouldn’t be [expletive] flying. There is a war going on,” he said. 

The Ukrainian president believed a "terrorist act" was the cause of the crash, his press secretary Svatoslav Tsegolko said. "Poroshenko thinks this of the plane that was brought down: it is not an incident, not a catastrophe, but a terrorist act." 

READ MORE: What is known about the Malaysian Airlines plane crash

Few weapons are capable of shooting down an aircraft at cruising altitude, but the strike is well within the range of Russian-made Buk surface-to-air missiles that are in the arsenals of both Ukrainian and Russian forces.

Buk missiles are mobile systems installed on wheeled or tracked vehicles that are designed to strike aircraft, cruise missiles, helicopters and other airborne targets.

The Russian state-run news agency Interfax speculated that the Malaysian airliner could have been mistaken for the personal plane of Russia's President Vladimir Putin, who was returning to Moscow from a BRICS summit meeting in Brazil on Thursday.

Watch: Aftermath of Malaysia Airlines flight MH17 disaster 

In a press conference early on Friday, Malaysian Prime Minister Najib Razak demanded swift justice for those responsible if the airliner was found to have been shot down.

“The Ukrainian authorities believe that the plane was shot down,” Najib said in the statement. “At this stage, however, Malaysia is unable to verify the cause of this tragedy. But we must, and we will, find out precisely what happened to this flight. No stone will be left unturned.”

“If it transpires that the plane was indeed shot down, we insist that the perpetrators must swiftly be brought to justice.”

Najib also said that Malaysia was sending a special flight to Kiev with a disaster assistance and rescue team.

“An international team must have full access to the crash site and no one should interfere with the area, or move any debris, including the black box,” he said.

Malaysia Airlines said air traffic controllers lost contact with Flight MH17 at 14.15pm GMT at 30 kilometres from Tamak waypoint, approximately 50 kilometres from the Russia-Ukraine border. Flight tracking data indicated it was at its cruising altitude of 33,000 feet (10,000 metres) when it disappeared.

Flight MH17 departed Amsterdam at 12.15pm local time and was estimated to arrive at Kuala Lumpur International Airport at 6.10am Malaysia local time the next day.

The downed Boeing 777-200ER jet, registered 9M-MRD, had a clean safety record, Malaysia Airlines said. It operated for exactly 17 years.

The loss of MH17 is the second disaster to hit Malaysia Airlines this year, following the mysterious loss of Flight MH370. It disappeared in March with 239 passengers and crew on board on its way from Kuala Lumpur to Beijing.

“This is a tragic day, in what has already been a tragic year, for Malaysia,” Najib said.

Australia's Prime Minister Tony Abbott he was "filled with revulsion" by this tragedy and put the blame on pro-Russian militants. More than 100 passengers on the plane were activists flying to Australia to attend the bi-annual World Aids Conference in Melbourne next week. 

READ MORE: Australian PM points finger at Russia over downed Malaysian plane

EU foreign policy chief Catherine Ashton called for an international investigation into the disaster.

“The circumstances must be clarified without delay and an international investigation needs to shine a light on this tragedy,” she added. “We call on all parties in the region to allow full access to the [crash] site.”

British Prime Minister David Cameron tweeted: “I’m shocked and saddened by the Malaysian air disaster.”

British media have reported that between five and 10 British citizens were on board MH17.

Holland’s Justice Minister Ivo Opstelten said “there were several Dutch onboard”, adding he was “deeply shocked” by the “horrible” images coming from the crash site. The flag at the Dutch embassy in Beijing stood at half-mast on Friday.

 

Distraught relatives of passengers were shielded from the media at Amsterdam’s Schiphol airport as news of the disaster spread.

A journalist saw several family members – many in tears – led into a restaurant on the upper deck of the airport, from where the ill-fated jet had departed hours earlier.

Shocked passengers due to catch a later flight to Kuala Lumpur, the destination of the downed plane, said they were determined to make their journeys.

“I’m going to board the plane. I’m sure the airlines are now taking precautions,” passenger Asri Strankina told reporters.

European air traffic control body Eurocontrol said that the route flown by MH17 "had been closed by the Ukrainian authorities from ground to flight level 320 [32,000ft] but was open at the level at which the aircraft was flying.”

Ukrainian aviation authorities have since closed airspace around Eastern Ukraine, Eurocontrol said. These routes are being rejected by Eurocontrol and will “remain closed until further notice.”

Unlike other Asian airlines, Malaysian Airlines did not reroute flights when Russian troops moved into Crimea earlier this year. From as early as the beginning of March, South Korea’s two main airlines, Korean Air and Asiana, as well as Australia’s Qantas and Taiwan’s China Airlines avoided Ukrainian air space.

Quizzed as to why Malaysia Airlines had not taken similar precautions, Malaysian Prime Minister Najib said international air authorities had deemed the flight path secure.

“The aircraft’s flight route was declared safe by the International Civil Aviation Organisation. And (the) International Air Transportation Association has stated that the airspace the aircraft was traversing was not subject to restrictions,” he said.

Re-routing would have involved a longer flight-time and therefore higher fuel costs.

Chris Beebe, the general secretary of the Hong Kong Aircrew Officers Association and a pilot for 33 years, said an aircraft's pilot, crew and the airline's operational team usually discuss and decide the best route for each flight. The airline took the ultimate decision to fly over eastern Ukraine, he said. "When a flight is dispatched a captain and crew will take into account the route of the flight and they’ll usually be briefed on potential conflicts along the way, he said."

Pilots will adjust their routing appropriately if they feel it’s an unsafe situation but that is usually done in conjunction with their dispatcher at the airline's operational control centre, said Beebe. "The routings of international flights are pretty detailed and it’s certainly all plotted out that it avoids potential conflicts," he said. 

Beebe said that the airplane's altitude depended on its load. "The airplane sounds like it was full. It therefore is not capable of going higher sometimes. A fully loaded plane with plenty of fuel potentially meant the Boeing 777 was unable to climb higher than 32,000-33,000 feet," he said. 

Hongkongers abroad can call the government's hotline at (852)1868 for help if needed.