A car bomb exploded outside the the Greek Central Bank in central Athens early Thursday, police said. No injuries have been reported.

The blast, which took place shortly before dawn, caused damage to nearby offices, stores and cars.

A warning telephone call had been made to a local daily and news website and police had immediately cordoned off the area. The police had yet to verify the phone call, in which the unidentified caller said the bomb contained 75 kilos of explosives.

No organization or group has yet claimed responsibility for the bomb attack.

The incident came at a time when Greece was set to make its return later Thursday to international bond markets for the first time since the beginning of the crisis in 2010 by offering five-year bonds to investors.