Jolted by a triple bombing in Athens, Olympic officials are looking afresh at security plans while stressing their confidence in the Games' hosts.

"The Games are an exposed event and so you have to be vigilant," French sports minister Jean-Francois Lamour said on Wednesday.

"It's a matter of being confident in the Greeks and adapting the (French security) plan."

The bomb attack targeted a police station just 100 days before the world's biggest sporting event was due to start, and a day after Greece said its security budget had been expanded by more than 50 per cent to over one billion euros.

"We remain as every other government does in constant contact and dialogue with the Greek government," British Prime Minister Tony Blair told parliament.

"Our present view is that the Games should go ahead as planned. We have every faith in the way the Greek authorities are handling this."

As the hosts of the first summer Olympics after the September 11, 2001 attacks on the United States, Greece is staging the biggest security operation in the 108-year history of the modern Games.

It will involve more than 45,000 armed guards. Greece has also asked NATO for help with air and sea patrols, and protection against weapons of mass destruction.

Nobody has claimed responsibility for the bombing. Greek police said initial evidence pointed to small local anarchist and leftist groups.

"SMALL INCIDENT"

"It's only a small incident," Dora Bakoyanni, the mayor of Athens, told reporters in Paris. "Things like this happen and I can assure you that everything has been put in place to guarantee everyone's security during the Games."

Last week Bakoyanni said she considered an attack on Athens during the August 13-29 Games unlikely.

A spokeswoman for the International Olympic Committee (IOC) said some national Olympic bodies had discussed safety concerns in the wake of the bombs, but had made no formal approaches to the IOC.

Greek and foreign security personnel will test safety plans from May 13 to 16 in a simulation of an attack on the Games. The French blueprint would be adjusted right up until the 28-sport event begins on August 13, Lamour said.

Australia, hosts of the last Games in 2000, said its spy agency would review security arrangements following the bombs. The Australian Olympic Committee said it was possible individual athletes would pull out.

"We would never stand in the way of any athlete making a personal choice in that regard," AOC secretary-general Bob Elphinston said.

Last week former U.S. swimming gold medallist Mark Spitz said the fear of a terrorist attack might spark a last-minute U.S. withdrawal from the Games, already dogged by controversy over delays in completing Olympic venues.

Spitz won gold at the 1972 Munich Olympics where an attack by Palestinian guerrillas killed 11 Israeli athletes. A bomb attack at the Atlanta Games in 1996 also killed one person.

"IMMENSE CONFIDENCE"

British IOC member and triple Olympic gold-winning rower Matthew Pinsent said the 2004 Games would be safe.

"(I have) immense confidence both in the Olympic authorities internationally and also the British Olympic Association (BOA)," Pinsent told BBC radio.

"You can bet your bottom dollar they're looking very closely at what's going on and how to ensure that the British team in isolation, as well as in the wider picture of the game, does well and is secure while they're out there competing.

"I'm completely sure the Olympic village is going to be very secure," Pinsent added.

Armed troops and police escorts will accompany teams to and from venues.

The Greek government will not allow foreign armed guards to accompany national teams on Greek soil and says it wants the city to be "open and pleasant" rather than feeling like a militarised zone during the Olympics.