Indonesian police on Saturday were studying DNA evidence from the remains of two suicide bombers who carried out twin attacks on luxury Jakarta hotels, as security was tightened across the country.
Suspected Islamist suicide bombers detonated powerful devices at the Ritz-Carlton and JW Marriott hotels in an upmarket business district on Friday, leaving nine dead and up to 50 injured including at least 18 foreigners.
A New Zealand businessman was confirmed dead and Australian Foreign Minister Stephen Smith, who is due in Jakarta later on Saturday, said he feared the worst for three missing Australians, including diplomat Craig Senger.
National police chief General Bambang Hendarso Danuri called on hotels and shopping malls across the vast, mainly Muslim archipelago of 234 million people to raise their security protocols amid warnings of follow-up attacks.
A military spokesman said 500 troops were on standby to deploy in Jakarta in support of police.
Police across the Philippines were also on heightened alert over fears homegrown Islamists could try to emulate the Jakarta bombings, and citizens were urged to report any suspicious behaviour or unattended baggage.
Hotels in New York were also increasing security although Police Commissioner Raymond Kelly said there was no information that a Jakarta-style attack was imminent.
US President Barack Obama condemned the bombings and offered Indonesia help in the recovery effort.
"I strongly condemn the attacks that occurred on Friday morning in Jakarta and extend my deepest condolences to all of the victims and their loved ones," he said.
Manchester United were due to stay at the Ritz-Carlton next week as part of an Asian tour but they cancelled the trip, denying a sell-out crowd of 100,000 the chance to see the English football giants play an Indonesia XI on Monday.
No group has claimed responsibility for the bombings, the worst in Indonesia since 2005, but suspicion inevitably fell on the Jemaah Islamiyah terror network responsible for the 2002 Bali attacks that killed 202 people.
Investigators said they found an unexploded bomb, as well as explosive chemicals and bomb-making materials in room 1808 of the Marriott, which they believe served as a control centre for the attackers.
The bombs were packed with nails, ballbearings, nuts and bolts to maximise the carnage, and appeared to be "identical" to ones previously used in JI attacks, police said.
They were also the same as bombs found in a recent raid on an Islamic boarding school in Central Java, carried out as part of the hunt for master-bombmaker Noordin Mohammed Top, leader of a JI splinter group.
Noordin is wanted for his role in the Bali attacks as well as a 2003 bombing at the Jakarta Marriott, which killed 12 people, and the 2005 truck-bombing of the Australian embassy in Jakarta.
President Susilo Bambang Yudhoyono, who was re-elected in a landslide on July 8, said the attack was an act of terror that would have "wide effects on our economy, trade, tourism and image in the eyes of the world".
Tourism operators on the Hindu-majority resort island of Bali said they feared for the lucrative tourism industry, which was just getting back to normal after the horrific attacks of 2002.
"I am afraid that the tourism sector which is now thriving in Indonesia would be affected significantly," Indonesian Chamber of Commerce and Industry representative for small businesses Sandiaga Uno told Anatara news agency.
"We hope that the bomb blasts would not deter foreign and domestic investors in making the investment in the country."
Tourism is one of the biggest sources of foreign capital for Southeast Asia's biggest economy, which has avoided recession in the global financial crisis, but needs more foreign investment to maintain its growth trajectory.
The country's mainstream Muslim groups joined Yudhoyono and world leaders in condemning the attacks, saying they could never be justified in Islamic teachings.
Condemnation poured in from around the world including from UN chief Ban Ki-moon, and from Indonesia's neighbours in Southeast Asia, where JI is accused of plotting to create a pan-Islamic state.