Indonesian police launched raids across the country on Friday following deadly coordinated attacks on Jakarta, saying they suspected a broader extremist network helped carry out an attack claimed by the Islamic State group.

The operations came as authorities ramped up security at public places following Thursday's combination of suicide bombings and shootings in the capital that left five attackers and two other people dead.

Confusion has reigned after the incident, with authorities struggling to provide concrete information on the shock attack that unfurled in daylight on a busy street lined with shopping malls, top hotels, and foreign embassies.

National police chief Badrodin Haiti told reporters the attack likely indicates the involvement of a broader support apparatus, and implying that conspirators might still be at large.

"The planners, financiers, and supporters that provide (explosive) materials, assemble the bombs, facilitate accommodations and vehicles etc... of course this is the work of a team that could be big or small," he said.

"This obviously was not conducted by five men, this takes teamwork."

Police said earlier on Friday that they had identified four of the five dead attackers, and launched raids by heavily armed officers in Jakarta and other locations across the far-flung archipelago that resulted in the seizure of an Islamic State flag and other unspecified "books and posters".

"We've sent teams to several cities for operations against targets we identified," he told reporters.

- IS faction blamed -

Unconfirmed reports have said the police dragnet resulted in some arrests, but these have not been confirmed by authorities.

Police are yet to release the names of those identified or other details, but said two of the dead militants were fugitive terrorism suspects.

But authorities in the world's most populous Muslim country have already placed blame for the attack on Katibah Nusantara, which police and terrorism analysts say is a faction of the ruthless Islamic State group that has carved out a self-proclaimed caliphate in Syria and Iraq.

It would mark the first attack in the region by Katibah Nusantara, which is made up primarily of Malay-speaking Indonesians and Malaysians.

Authorities in Southeast Asia with significant Muslim populations have repeatedly warned of the potential for their citizens to return from IS jihad and carry out violence at home.

Indonesian police were put on their highest alert Friday, with security stepped up at some foreign embassies, and officers in Jakarta and on the resort island of Bali patrolling in riot gear and with assault rifles.

The rapid-fire series of bombings and a shootout between gunmen and police erupted in the centre of the capital, shocking moderate Muslim Indonesians.

The two victims of Indonesia's worst terror incident in seven years were a Canadian and an Indonesian man, according to police. Two dozen other people were wounded -- three foreigners, six police officers and the rest Indonesian civilians.

The attacks spilled out in dramatic fashion on a bustling street at mid-morning, transfixing Indonesia's hyperactive social media world, as images and videos of the carnage went viral.

Police have singled out Indonesian extremist Bahrum Naim, believed to be a founding member of Katibah Nusantara, as orchestrating the operation.

Indonesian police have explicitly likened the attack to the far bloodier violence in November in Paris that left 130 people dead and offered sobering proof to a horrified world of the reach and fanatical determination of IS jihadists.

- 'Stupid terrorists' -

The attack centred on a downtown Starbucks outlet, where a suicide bomb was detonated. Two men on a motorbike also destroyed a police post in another suicide bomb attack that left four officers severely injured.

Starbucks has closed all outlets in Jakarta until further notice.

Indonesia suffered several large bomb attacks by Islamic radicals between 2000 and 2009, but a subsequent security crackdown weakened extremist networks, and there had been no major attacks since 2009.

President Joko Widodo has urged calm, and there seemed little evidence of public jitters, with Jakarta back to its bustling self on Friday, the Muslim holy day.

"I am not afraid of terrorists because life is in Allah's hands, and today is Friday so, God willing, nothing bad will happen," said Toto Suhadi, 52, a gardener watering plants near the attack site.