(CNN) -- A strong bomb blast shook one of the main courthouse buildings in central Athens on Thursday morning, Greek police said.
Also Thursday morning, a bomb exploded in front of the Greek Embassy in Buenos Aires, Argentina. It is not known whether the blasts are linked.
The explosion in Athens 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 plate 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.
In the Argentine capital, no one was injured in the blast at the Greek embassy, the state-run Telam news agency reported.
The explosion happened about 2 a.m. (midnight Wednesday ET), police said, according to Telam. The bomb was left at the entrance to the embassy. The blast broke some windows on the embassy building and other properties on the block, the news agency reported.
Journalist Elinda Labropoulou contributed to this report.