Army trucks thundered through Indonesia's capital on Friday as authorities boosted security at possible terror targets and probed a suspected Islamic State cell blamed for Jakarta's deadly terror attacks, reports AFP.

A series of bombings and subsequent gun battles on Thursday between the attackers and police in a busy part of the capital lined with malls and foreign missions left two civilians and five attackers dead.

Police in the world's most populous Muslim country have blamed the carnage on a network of Islamic State fighters from Southeast Asia forged in the radical jihadist group's war in Syria and Iraq.

"An alert has been imposed throughout Indonesia," said national police spokesman Anton Charliyan.

"National police are on their highest alert, especially in areas considered targets of terror, like police stations, government offices, embassies, with army backup."

He did not elaborate on the army's role but AFP reporters saw a passing convoy of a half-dozen military trucks filled with heavily armed soldiers in central Jakarta, and heightened security elsewhere, with police patrolling in flak jackets.

A police car and a half-dozen officers were seen guarding the French embassy near the attack site.

Raids planned

Charliyan added police would be conducting raids Friday as they probe those responsible for the bloodshed, which spilled out in dramatic fashion on a bustling street in the mid-morning.

He declined to offer further details on the planned raids.

The assault left five attackers, a Canadian and an Indonesian man dead and 20 others injured, according to police, in what the country's president called "acts of terror".

Police have singled out Indonesian extremist Bahrum Naim as being behind the planning.

Naim, believed to be in Syria, is said by authorities to be a founding member of Katibah Nusantara, the grouping of Southeast Asian fighters there.

Terror analysts warn that the group, believed to include fighters predominantly from Indonesia but also Malaysia and elsewhere in the region, has threatened for more than a year to bring the jihad home.

Indonesian authorities were yet to offer concrete details from their investigations.

Muhammad Iqbal, Jakarta's police spokesman, told AFP authorities were working to establish the identities and connections of the dead attackers.

Growing fears

The Islamic State group claimed the attack was carried out by its "soldiers" against citizens from the "crusader coalition", referring to the US-led alliance combating the jihadists.

Fears have grown in Indonesia and other parts of Southeast Asia with Muslim populations that a wave of extremist violence born in Syria could return to home shores.

Police said the five-strong cell that struck Thursday included three suicide bombers who initially targeted a Starbucks near a major shopping mall.

Men armed with pistols then took two foreigners hostage -- an Algerian and a man Ottawa said they had been told by Indonesian authorities was a Canadian.

The Algerian escaped with bullet wounds, police said, but the second man was shot dead.

Two men on a motorbike also ran into a police post, blowing themselves up and leaving four officers in critical condition.

Indonesian police have said the attack followed the pattern of the Paris attacks in November that left 130 people dead.

Starbucks said it was shutting all branches in the Indonesian capital until further notice.

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