A strong bomb blast shook one of the main courthouse buildings in central Athens on Thursday morning, Greek police said, according to CNN.

The explosion occurred about 40 minutes after an unidentified person placed warning calls to a local TV station and newspaper, saying a bomb would explode outside the "administrative first instance courthouse." The advance notice gave police enough time to evacuate the building.

Police said the blast came from a motorbike rigged with explosives that was parked in the median across from the courthouse in the Ambelokipi district. The caller provided the place number on the bike.

A cloud of smoke was visible in the area and there was some damage to the front of the building and nearby cars from the explosion.