Media captionJakarta's Police Chief Tito Karnavian said the terror problem was "not home grown"
Jakarta's chief of police has said Indonesia is hunting terror cells believed to be behind Thursday's attack on the capital.
Two civilians and five attackers died in the gun and bomb assault in a busy commercial district.
Insp Gen Tito Karnavian said the attackers had been "neutralised" but were linked to groups across Indonesia and were "part of a global network".
The Islamic State (IS) militant group has said it was behind the attack.
It released a statement online saying it had been carried out by "soldiers of the Caliphate", targeting "citizens of the Crusader coalition" against the group.
Three men were arrested near Jakarta early on Friday, police told local media. It was not immediately clear whether they had direct links the attacks.
Authorities have named Bahrum Naim, an Indonesian believed to be fighting with IS in Syria, as the suspected co-ordinator.
Insp Gen Karnavian said Naim's "vision" is to unite the various IS-supporting groups across South East Asia.
Indonesia - which has been attacked by Islamist militants several times - had been on high terror alert following recent threats issued by IS.
Security forces battled militants for hours on Thursday in a major business and shopping district of Jakarta.
The assault ended when two of the attackers were killed in a suicide bombing, said police, with the other three killed in gun battles.
A Canadian and an Indonesian national, both civilians, also died and at least 20 people were injured. 'Game-changer' for Indonesia - Ali Moore, BBC News, Jakarta
Life is getting back to normal on the junction where the attack happened - but only up to a point.
Traffic is flowing and the road sweepers are busy, but the police post which was hit remains boarded up, and the Starbucks cafe at the centre of the attack is surrounded by iron fencing, curious onlookers and media using anything at hand to peer over the top at the blown out windows.
The condolence flowers have now been removed - probably to stop the crowds gathering to take selfies, risking their lives in the morning traffic.
But with the city's police chief admitting Thursday's assault is likely a game-changer for Indonesia, there is no doubt the risk of another attack has taken a new form. And no matter how "tiny" the group, as he called them, they have proved they can kill. Insp Gen Karnavian told the BBC that main culprits had been "neutralised" but were "connected to other cells in Java and Sulawesi and we are chasing them".
He said one IS plot had been foiled at the end of 2015 and a number of people detained, among them a man who said he had been instructed by Naim.
Naim has been linked to the IS-allied East Indonesia Mujahidin Group (MIT), which is based on the island of Sulawesi.
The police chief said Indonesia had significantly developed its understanding of domestic terror networks since the 2002 bomb attack in Bali, which killed 202 people.
Some 1,000 people linked to radical networks had been brought to justice in Indonesia since 2000, he said, but some had since been released from prison and had "the potential to pose a threat".
"What we need to do today is strengthen capability and also sharing information with others because it is not home grown in Indonesia but it is part of a global network," he said.
Indonesian President Joko Widodo has condemned the attacks as "acts of terror".
He tweeted on Friday that there was "no place for terrorism on Earth" and that "every citizen in the world" needed to fight it.
Media captionA history of militancy in IndonesiaIndonesia has suffered militant attacks in the past, but has been relatively successful in curbing home-grown Islamist extremism after a spate of attacks in the last decade. Some of the deadliest include:
July 2009: Seven people killed and dozens wounded when two suicide bombers target Marriott and Ritz Carlton hotels in Jakarta
Oct 2005: Suicide attacks in Bali leave 23 dead, including the bombers
Sept 2004: Bomb outside Australian embassy in Jakarta kills at least nine people
Aug 2003: Bomb at Jakarta's Marriott Hotel kills 12
Oct 2002: Bali bombings kill 202, including 88 Australians
Dec 2000: Church bombings across the country kill 19
Media captionEyewitness Jeremy Douglas: "We heard a third [explosion]...a fourth, a fifth, a sixth"
A series of bomb blasts have rocked the Indonesian capital, Jakarta, with continuing gunfire and reports of further explosions.
At least six people have been killed by the blasts, say police, which hit locations including a shopping centre close to UN offices.
Police say at least four suspected attackers are dead. It remains unclear who was behind the assault.
President Joko Widodo has called for calm but condemned the "act of terror".
"We all are grieving for the fallen victims of this incident, but we also condemn the act that has disturbed the security and peace and spread terror among our people," he said.
LIVE coverage of Jakarta attacks Image copyrightAFPImage caption Police have been taking shelter behind cars amid continuing gunfire National police spokesman Anton Charliyan told local media police officers and civilians were among the dead and that no arrests had been made.
Images from Jakarta showed several bodies lying on the road outside a cafe and police police, as well as seriously injured people being carried away.
Indonesia has been attacked by Islamist militant groups in the past and was on high alert over the new year period after threats from the so-called Islamic State (IS).
Mr Charliyan said while it was not yet clear who carried out the attack, IS had warned of a "concert in Indonesia" which would be international news.
'Gunfire right now'
Image copyrightAPImage caption Heavily armed police are on the streets of the capital The attack began with initial blasts outside the Sarinah shopping centre in Jakarta, followed by more than an hour of gunfire and continuing reports of further explosions.
Armed police, snipers and armoured vehicles are on the streets of the capital.
BBC Indonesian reporter, Jerome Wirawan said police had cordoned off the area around the shopping centre. Image copyrightAFPImage caption There were reports of police chasing suspects Image copyrightAPImage caption Police urged people to stay indoors in case of further explosions Image copyrightEPAImage caption At least one police officer was injured inside the Starbucks cafe Image copyrightEPAImage caption Police cordoned off the area around the cafe A UN official, Jeremy Douglas, told the BBC he was about 150m away from one of the first blasts near the UN's building.
"Then we ran into the building. We heard a third explosion. We got up to our office on the tenth floor and we heard a fourth, a fifth and a sixth."
In one incident eyewitnesses say at least three attackers entered a Starbucks cafe in the area, which is close to several embassies, and detonated explosives before opening fire.
A Reuters photographer said police appeared to be aiming guns at a man on the roof of the building. 'Maximum damage': Karishma Vaswani, BBC News
Jakarta police have been saying for some time that an attack on Indonesian soil may be just a matter of time.
Although it isn't yet clear who is behind these attacks, they appear designed to inflict maximum damage.
Although no-one has claimed responsibility for these attacks, in the last few years there have been anywhere between 150-200 Indonesians who it is thought have gone to Syria to fight with IS.
Many have since returned and the police have thought that they might be preparing an attack in Indonesia.
Indonesia is the world's most populous Muslim nation but by and large is secular, although in recent years the threat of radicalism has remained high as small networks of militants are still thought to be operating in the country. Are you in Jakarta? Have you been affected? If it is safe to do so, let us know about your experiences. Email haveyoursay@bbc.co.uk with your stories.
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