ATHENS, Greece- Police in Greece say a powerful bomb has exploded outside a closed night club in Athens, causing no injuries, in an attack linked with criminal extortion groups.

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A police statement says the pre-dawn blast occurred just before 4 am(0200 GMT) Friday near the city center. The explosion was heard across southern Athens and severely damaged the club's facade.

The investigation is being handled by the police department responsible for extortionists, who have carried out several similar attacks in recent years.

On Thursday, suspected radical anarchists exploded a strong bomb outside an Athens administrative court, causing severe damage but no injuries. A warning call before the blast allowed police to evacuate the area.