Athens  - A strong explosion shook central Athens after a car bomb went off Thursday on a busy avenue, causing serious damage but no injuries, the state news agency said.

The car bomb exploded outside the building of the State Property Company, a short distance from Athens' central police headquarters and Greece's supreme court, damaging nearby cars and buildings.

There was no warning prior to the explosion and no group claimed responsibility for it.

Greece has been plagued by daily bombings and arson attacks on banks and multinational businesses since the shooting of a teenager in December, which sparked the worst riots the country has seen in decades.

Experts fear that the militant group Revolutionary Struggle, which recently claimed responsibility for bomb attacks on two Citibank branches, and the new Sect of Revolutionaries have recruited fresh members since those riots and have acquired large quantities of arms and explosives.

Revolutionary Struggle has claimed responsibility for a number of attacks against government offices and police, including a rocket attack against the US embassy in Athens in 2007.

The violence has embarrassed Prime Minister Costas Karamanlis' government, which has been criticized for its inability to protect citizens. dpa