A major power failure hit Athens and other parts of Greece on Monday, exactly one month ahead of the opening of the home-coming Olympic Games, cutting off air conditioning as a heatwave sweeping the Mediterranean country and pushing the temperatures past 40C.

The power blackout was not due to a shortage of power but because the electricity grid became overloaded as a result of higher-than-average demand due to the rare heatwave, Greek authorities said.

The blackout hit more than 75 percent of greater Athens, the host city of Olympic Games, and appeared to have quickly spread to the southern part of Greece, police said.

Sensitive locations, such as Olympic venues, were immediately put on emergency power supply.

A center of Validation for Olympic Accreditation Card, close to the Main Press Center (MPC) for the Olympic Games, was blacked out when the staff were preparing to verify the media accreditation cards for journalists from Xinhua shortly before 1 pm local time.

The electrically-powered trains of the Athens metro and the Kifissia-Piraeus light railway stopped running and a number of passengers were caught in between stations, though all were extricated within 12 minutes without particular problems, police said.

Transport Minister Mihalis Liapis was also a victim of the power failure during a test run of the metro service to the Athens international airport and has asked Prime Minister Costas Karamanlis for additional power to all rail services so that they do not stop running during future crises of this kind, local media reported.

The power failure caused extensive problems with traffic lights throughout south and central parts of the country, particularly in highly congested areas like the capital, while the fire brigade received over 500 calls to help people stuck in elevators.

The Greek government has pledged to International Olympic Committee officials that no power cuts would happen during the Olympic Games slated for August 13-29.

However, the electrical grid collapse raised questions about Athens' ability to handle increased power demands during the two-week games.