Indonesia has introduced tough new security measures following a devastating car-bomb attack in the capital, Jakarta.
The massive explosion killed at least 13 people
At least 13 people, including one foreigner, have been killed while another 150 from a range of nationalities have been injured.
The blast severely damaged five floors of the luxury US-run Marriott Hotel, shattering glass and damaging cars parked outside.
The BBC's Rachel Harvey says it is not yet clear who was behind the attack, but suspicion will inevitably fall on the group also blamed for the Bali bombings, an extremist Islamic organisation called Jemaah Islamiah.
The governor of Jakarta, Sutiyoso, said the explosion was "very likely" to have been carried out by a suicide bomber.
Police chief General Da'i Bachtiar said there were similarities between Tuesday's attack and the devastating blast in Bali last October which left 202 people dead.
In the Bali attack, a suicide bomber detonated his bomb moments before an explosives-laden van blew up across the street.
The government has ordered an immediate strengthening of its anti-terrorist laws and also invited the Australian police to help in the hunt for those responsible.
Indonesian President Megawati Sukarnoputri, who recently vowed to destroy terror networks in the world's largest Muslim nation, visited the scene of the attack late on Tuesday.
The United States urgently renewed its calls for Americans in Indonesia to follow tighter personal security measures.
Tuesday's blast came just two days before the expected verdict in the trial of a key Bali suspect, Amrozi bin Nurhasyim.
Security has been tight in Indonesia since the Bali bombings, and authorities have warned of similar threats.
The huge blast at the hotel, which is well known as a place where foreigners and visiting diplomats stay, came during a busy lunchtime in the commercial part of city.
Police say the bomb is thought to have been inside a Toyota van parked outside the lobby of the hotel, which is located near foreign embassies and office blocks.
The lower floors of the building were gutted and the windows above were blown out, right up to the 21st floor.
Eyewitnesses described a scene of horror, with people fleeing the flames engulfing the building, some already burned, others bleeding.
The remnants of uneaten meals at the local cafes and restaurants were left scattered across the floor.
The Dutch citizen killed in the blast was Hans Winkelmolen, 49, president of PT Rabobank Duta Indonesia, a subsidiary of the Dutch co-operative bank Rabobank.
He had been in Jakarta since 2000 and was preparing to follow his family back home to the Netherlands later in August.