Police and anti-terrorist experts gather outside the U.S. embassy in Athens following a rocket attack yesterday. An explosion caused by a rocket attack rocked the U.S. embassy in central Athens early yesterday, but no injuries were reported, Greek police said. --Xinhua

Greek authorities yesterday began to investigate the attack on the U.S. embassy in Athens, local media reported.

The U.S. Embassy in Athens was attacked early yesterday by a rocket that exploded inside the modern glass-fronted building of the embassy but caused no casualties.

Public Order Minister Vyron Polydoras condemned "this act of violence with a strong sense of abhorrence," saying the attack is a symbolic "attempt to disrupt our country's international relations."

"It is very likely that this is the work of a domestic group," Polydoras said, adding "we believe this effort to revive terrorism is deplorable and will not succeed."

The minister underlined the solidarity between the Greek government with the U.S. government, saying the Greek authorities are thoroughly investigating the case in order to ensure those responsible arrested and impeached.

He also confirmed earlier reports that two phone calls had been placed by unidentified callers, one of which claimed responsibility for the attack on behalf of the shadowy ultra-leftist terror gang "Revolutionary Struggle".

All possibilities are being investigated, the minister added.