Japanese Olympic officials are compiling an emergency manual to help their athletes in the event of a terrorist attack at the Athens Games in August.

However, the Japanese Olympic Committee (JOC) said on Thursday that there were no immediate plans to increase security following Wednesday's bomb blasts in the Greek capital.

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"We are quite aware of the possibility of terrorist acts during the Olympics," the JOC's public relations manager Toru Watanabe told Reuters.

"Of course we're concerned and it will be important to be prepared. We are putting together a manual to instruct athletes how to act in an emergency."

Three bombs exploded in Athens on Wednesday, just 100 days before the start of the Olympics on August 13, raising fresh safety concerns about the world's biggest sporting event.

However, Watanabe said the JOC would not be seeking the advice of the Japanese government unless the security situation in Athens deteriorated.

"We believe the Greek police and Olympic organisers will make every effort with security measures," he said.

"At the moment we don't know who is responsible (for Wednesday's explosions) and what their motives were, so we have no plans to talk directly to the Japanese government."

Australia is considering sending armed guards to Greece and having planes on standby to evacuate its athletes in the event of an attack.

Asked if Japan could follow suit, Watanabe said: "Not at this stage. Our manual will impress upon the athletes the need to be vigilant as well as who to contact in the case of an emergency."