At least three suicide bombers exploded themselves in a Starbucks cafe in downtown Jakarta on Thursday while two gunmen attacked a police post nearby, a witness told The Associated Press. TVOne, a local television network, reported three other explosions in other parts of the city.
At least one policeman was killed in addition to the bombers.
The first explosion appeared to have triggered a gun-battle between the attackers and anti-terror police squads, and gunfire could be heard more than 1 ½ hours later.
Tri Seranto, a bank security guard, told The Associated Press he saw at least five attackers, including three suicide bombers who exploded themselves in the Starbucks.
He said he was out on the street when he saw the three men entering Starbucks and saw them blowing themselves up one by one. He said the other two attackers, carrying handguns, entered a police post from where he heard gunfire. He said he later saw one policeman dead and three seriously wounded.
He said he was not injured in the explosions as he was a little distance away, but close enough to witness the attack at 10.30 a.m. (0230 GMT).
He said the two gunmen ran away with police chasing them.
No one has claimed responsibility for the attacks.
Gunshots were heard after the midmorning explosion in front of the Sarinah shopping mall and a police station. The area also has many luxury hotels, and offices and embassies, including the French. The other set of explosions were in neighborhoods where the embassies of Turkey and Pakistan are located.
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."
Indonesia has been a victim of several bombing attacks in the past, claimed by Islamic militant groups.
Last month, anti-terror police arrested nine men and said the group had wanted to "perform a 'concert' to attract international news coverage of their existence here." Police cited a document seized from the group that described the planned attacks as a "concert."
The country has been on high alert after authorities said they had foiled a plot by Islamic militants to attack government officials, foreigners and others. About 150,000 police officers and soldiers were deployed during New Year's Eve to guard churches, airports and other public places.
More than 9,000 police were also deployed in Bali, the site of Indonesia's deadliest terror attack, which killed 202 people in 2002.
National Police spokesman Maj. Gen. Anton Charliyan said security is focused on anticipating attacks in vulnerable regions, including Jakarta.
On Tuesday, the jailed radical Islamic cleric Abu Bakar Bashir appealed to an Indonesia 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 by the Jemaah Islamiyah network in the past. But strikes in recent years have been smaller and less deadly, and have targeted government authorities, mainly police and anti-terrorism forces.