Depok area police chief Col. Dwiyono told MetroTV that the men were arrested at dawn at their homes in Depok on the outskirts of Jakarta.

Dwiyono, who goes by one name, says the men are suspected militants and are being questioned over possible links to the attack Thursday that killed seven.

MetroTV broadcast footage of the handcuffed men being escorted by police.

READ MORE: Revealed: the former cafe manager suspected of masterminding Islamic State attack on Jakarta

According to Coordinating Minister for Political Legal and Security Affairs Luhut Pandjaitan, the attack began with an explosion inside a Starbucks cafe in the Menara Cakrawala building, near the popular Sarinah department store.

“A suicide bomber entered the Starbucks and blew himself up,” Pandjaitan told reporters. A Jakarta-based private television network aired footage showing the body of a suicide bomber inside the cafe.

A photo circulating on social media also showed a Caucasian man lying in front of the door of the Starbucks.

Tomi Sucipto, a spokesman of the U.N. Development Program, confirmed that the man, a Dutch citizen, is a staffer of the organisation and said he is undergoing surgery at an army hospital.

READ MORE: United Nations official describes chaos as horrifying militant attack unfolds in Indonesia’s capital

Following the first blast, Pandjaitan and Deputy National Police Chief Budi Gunawan said another group of suicide bombers attacked a police box located at an intersection near Sarinah. Photos posted on Twitter showed three men lying on the road next to the police box.

Gunfire later occurred in the parking area of the Menara Cakrawala building during which police shot dead two attackers, Budi said.

Pandjaitan confirmed that a total of five blasts occurred including suicide bombings.

“We are still chasing after two perpetrators on a motorcycle carrying rifles,” National Police spokesman Anton Charliyan said, adding that an exchange of gunfire with the duo was ongoing in the Palmerah area in West Jakarta.

WATCH: A chaotic day captured live on television

Islamic State officially claimed responsibility on Thursday night for the gun and bomb assault.

“A group of soldiers of the caliphate in Indonesia targeted a gathering from the crusader alliance that fights the Islamic State in Jakarta through planting several explosive devices that went off as four of the soldiers attacked with light weapons and explosive belts,” the group said in a statement.

The attacks followed several warnings in recent weeks by police that Islamic militants were planning something big. It was unclear if any perpetrators remained at large.

Gen. Anton Charilyan, a national police spokesman, said the attack involved an unknown number of assailants with grenades and guns, imitating the recent “terror acts” in Paris.

Chinese Ministry of Foreign Affairs Hong Lei said China is shocked to learn of the attack and condemned perpetrators.

A staff member with China embassy in Indonesia said no Chinese national has been hurt during the attack after communicating with local police. As of now, the office has yet to receive any request of assistance from Chinese tourists travelling in the city.

A spokeswoman for the Security Bureau said on Thursday they have no plans to raise a travel alert for Indonesia currently but would continue to monitor the latest developments.

Hong Kong has maintained an amber travel alert for Indonesia since July 2009 when bombings of two hotels killed seven people and injured more than 50.

The amber warning is the lowest of the Hong Kong government’s three-tier outbound travel alert system suggesting signs of threats for travellers in the country. Hongkongers intending to visit or already there are advised to exercise caution.

Hong Kong’s Immigration Department said it had not received any calls for assistance from any Hongkongers affected by the blast so far. The department said it will continue to liaise with the Chinese Embassy in Indonesia to monitor the situation.

WATCH: Witness recounts shooting in deadly Jakarta attack

Aoura Lovenson Chandra, 33, an Indonesian Chinese filmmaker based in Jakarta, said fear remains after the attack has been contained.

“This seems to be a random attack comparing to previous bombings with specific targets like the Australian embassy or the J.W. Marriot Hotel. This attack worries me more than the previous ones because it’s hard to avoid as it’s on a regularly used main road, a close part of our daily lives,” Chandra told the South China Morning Post in a phone interview.

“But life must go on so we can only remain vigilant for now,” he said.

Another 26-year-old student Wenny Astaria in Jakarta expressed grief over the tragedy but she is confident with the handling of local government and police.

“I’m not scared, Jakarta is still a safe place,” she said.

Before 2009, bombings at nightclubs on the resort island of Bali in 2002 killed 202 people, mostly foreigners.

No one claimed responsibility for Thursday’s attack on Thamrin Street, which prompted a security lockdown in central Jakarta and enhanced checks all over the crowded city of 10 million.

Charilyan said police had received information in late November about a warning from the Islamic State group that “there will be a concert” in Indonesia, meaning an attack.

“This act is clearly aimed at disturbing public order and spreading terror among people,” President Joko Widodo, said in a statement on television.

He has visited the site of the attacks and conveyed condolences for the families of the victims.

Widodo, who was in the West Java town of Cirebon, cut his trip short soon after being informed about the attack.

“The state, the nation and the people should not be afraid of, and be defeated by, such terror acts,” he said.

Tri Seranto, a bank security guard, told The Associated Press he saw at least five attackers, including three who triggered explosions at the Starbucks. It was not immediately clear if they exploded bombs or grenades.

Tri described them as suicide bombers, but police spokesman Charilyan denied they blew themselves up.

He said the two dead civilians were a Dutch citizen and an Indonesian. An Algerian man was among the 10 injured, he said.

WATCH: Video shows Starbucks blast in Jakarta

But there was some confusion about the Dutch citizen’s status. A Dutch Foreign Minister spokeswoman in the Netherlands said he was seriously injured and was undergoing surgery.

After the explosions at Starbucks, a gunbattle broke out between the attackers and anti-terror police squads, and gunfire could be heard more than 1½ hours later.

Witnesses saw at least three bodies sprawled on the sidewalk after the fighting ended.

The area has many luxury hotels, and offices in high-rise buildings and embassies, including the French.

WATCH: Video said to be of gunman in Central Jakarta firefight

Tweets from the account of Jeremy Douglas, regional representative of the United Nations Office on Drugs and Crime for Southeast Asia and the Pacific, described a bomb and “serious” exchanges of gunfire on the street outside his Jakarta office. “Didn’t experience this in 3.5 years in #Pakistan,” he wrote.

“A massive #bomb went off in front of our new #Indonesia office as @collie_brown & I exit car. Chaos & we're going into lock-down,” he wrote. And three minutes later: “Apparent #suicidebomber literally 100m from the office and my hotel. Now gunfire.”

About 30 minutes after his first post about the bombing, he posted that things were “quiet. Not comfortable quiet.”

Police were “sterilising” a theatre building close to the initial bombing site suspected as the hiding place for the terrorists.

“We are sterilising the building from basement to top,” Iqbal Kabid told reporters, according to The Guardian.

He said that a gunbattle between the attackers and police took place in the cinema in the same building as a Starbucks cafe that was attacked.

“We will declare the situation secure soon,” he said.

Last month, anti-terror police arrested nine suspected militants and said they had planned attacks “to attract international news coverage of their existence here.”

The country has been on high alert after authorities said they foiled a plot by Islamic militants to attack government officials, foreigners and others. About 150,000 police officers and soldiers were deployed on New Year’s Eve to guard churches, airports and other public places.

More than 9,000 police were also deployed in Bali.

On Tuesday, jailed radical Islamic cleric Abu Bakar Bashir appealed to a court to have his conviction for funding a terror training camp overturned, arguing that his support for the camp was an act of worship.

The 77-year-old leader of the Jemaah Islamiyah militant network filed a judicial review of his 2011 conviction, when he was sentenced to 15 years in jail for setting up the camp in Aceh province. A higher court later cut the sentence to nine years.

Indonesia, the world’s most populous Muslim nation, has suffered a spate of deadly attacks blamed on the Jemaah Islamiyah network in the past. But militant strikes in recent years have been smaller and less deadly, and have targeted government authorities, mainly police and anti-terrorism forces.

Additional reporting by Mimi Lau, Reuters and Agence France-Presse