The blast hit just after midday, the car bomb ripping through the 5-star hotel in central Jakarta.

The American Marriott Hotel is located close to embassies and other foreign interests. It's been a favourite location for visiting heads of state, including Australian Prime Minister, John Howard.

The Prime Minister preferred to emphasise that the target was Indonesia and not the Western world.

JOHN HOWARD, AUSTRALIAN PRIME MINISTER: Although it took place outside a hotel which is frequented by Westerners and seen as something of a Western symbol, the victims were the men and women of Indonesia.

It was Indonesian hotel workers and taxi drivers parked outside who bore the brunt of the massive explosion. Nothing could diminish the shock, but the attack, a suspected suicide bombing, was not exactly a surprise.

ALEXANDER DOWNER, AUSTRALIAN FOREIGN MINISTER: To the best of my knowledge we didn't have any specific information in relation to the Marriott Hotel, but of course we've been concerned about possible attacks and our travel advisory has warned Australians to defer all non-essential travel to Indonesia and has also warned of the possibility of terrorist attacks including in international hotels, so this sort of incident is the sort of incident that we'd have to say is very tragic but was not entirely unexpected.

The threat of an attack has loomed large since last October. The Bali blasts were the handiwork of the radical group Jemaah Islamiah, now the prime suspect in yesterday's bombing.

COMMISSIONER MICK KEELTY, AUSTRALIAN FEDERAL POLICE: It does have at this early stage all the hallmarks of Jemaah Islamiah. They have the motive, they have the intention and they have the capability.

And there are links between yesterday's blast and other events, which may well be more than a coincidence.

On the day of the explosion in Jakarta, the spiritual leader of Jemaah Islamiah, Abu Bakar Bashir, was giving evidence at his treason trial, streets away from the Marriott. And in another link, the man accused of masterminding the Bali bombing, Amrozi is being sentenced for his crime tomorrow.

ALEXANDER DOWNER: Whether this explosion took place because of those events, you just don't know at this stage. It's possible.

Terrorism experts warn that, despite a series of arrests, the region may have to brace itself for further violence.

ROHAN GUNARATNA, INSTITUTE OF DEFENCE AND STRATEGIC STUDIES: The message is very clear - if you are not going after the leadership of JI, they are going to strike you again. They will do, and attack even worse than what we have seen in Bali or in Jakarta.

There are doubts that President Megawati Sukarnoputri is capable of controlling political extremists in her country. And there are fears that a crackdown may inspire a further backlash.