Malaysian Prime Minister Najib Razak says the leader of pro-Russian rebels in eastern Ukraine has agreed to hand over both "black box" flight data recorders from downed Malaysia Airlines flight MH17 to investigators from his country.
Najib also said that the remains of 282 of the 298 crash victims were being moved by train to the city of Kharkiv in eastern Ukraine, where they would be handed over to Dutch authorities. The remains would then be flown to Amsterdam.
Watch: Ukraine rebels hand over MH17 black boxes
Nearly 200 of those killed when the Boeing 777 was shot down over eastern Ukraine on Thursday by a missile apparently fired by rebels were Dutch.
The flight, a code share with Dutch flag carrier KLM, was bound from Amsterdam to Kuala Lumpur.
Najib also said independent international investigators had been guaranteed safe access to the crash site to begin a full investigation.
On the ground, the animosity between Ukraine's warring sides was underlined by intense shelling which erupted in the rebel stronghold of Donetsk, a city just 60km from the station in the village of Torez where, until yesterday, the bodies had been held in refrigerated railway wagons.
Artillery fire sent plumes of smoke skywards in what the separatists said was an attempt by government forces to enter the city they seized in April. The clashes quickly subsided.
In Washington, President Barack Obama demanded that international investigators get full access to the crash site and accused the separatists of removing evidence.
"What exactly are they trying to hide?" he asked, a day after the United States presented what it called "powerful" evidence that the rebels shot down the plane with a Russian surface-to-air Buk missile.
At the UN in New York, the Security Council was poised to vote on a resolution proposed by Australia demanding international access to the crash site and a ceasefire around the area.
European leaders have signalled they could ramp up sanctions against Russia as early as today, barely a week after a new round of sanctions was imposed.
Whole sectors of the economy, including goods with possible military uses, could be targeted, British Prime Minister David Cameron said.
The pressure has been growing on Russian President Vladimir Putin, who the US and others say has backed and armed the rebels, to rein in the insurgents in Ukraine and allow a full-scale investigation. The rebels have been blamed around the world for last Thursday's downing of the airliner.
Putin lashed out at the criticisms, accusing others of exploiting the crash for "mercenary objectives".
Later Moscow challenged Kiev, saying records showed a Ukrainian military plane had been flying just three to five kilometres from the Boeing 777.
"With what aim was a military plane flying along a civilian aviation route practically at the same time and at the same flight level as a passenger liner?" asked Lieutenant General Andrei Kartopolov.
Watch: Train with MH17 victims to only leave under OSCE control: "Prime Minister" of self-proclaimed People's Republic of Donetsk
At the Torez railway station, an overpowering stench filled the air as Dutch investigators opened each of the wagons holding the bodies of victims.
Michael Bociurkiw, a spokesman for the Organisation for Security and Cooperation in Europe, said the group's investigators believed some bodies had been incinerated without a trace.
Associated Press, Reuters, Bloomberg