Gunmen fired a rocket at the American embassy in the Greek capital, Athens early Friday morning, causing damage but no injuries. VOA's Sonja Pace reports from our London bureau, Greek police are calling it terrorism and authorities blame a leftist Greek militant group.

The rocket hit the heavily fortified embassy building shortly before 6 am local time. It was apparently fired from a vacant building site across the street from the embassy.

U.S. Ambassador Charles Ries told journalists in Athens that the rocket caused some damage. He said the embassy building was occupied at the time, even though staffing was minimal that early in the morning.

Police guard the entrance of the U.S. Embassy in Athens after unknown assailants fired a rocket into the facility early 12 Jan 2007

"There can be no justification for such a senseless act of violence. Good news is that no one was hurt, minimal damage," he said. I" have talked to the minister of foreign affairs. She has assured me that the government will do all it can to find who did this, how it was done."

The embassy is closed for the day and the site has been cordoned off.

Greek police quickly labeled the attack an act of terrorism and authorities blamed domestic extremists. They said they had received claims of responsibility from at least one leftist militant group, the Revolutionary Struggle. The group has claimed responsibility for several attacks in recent years.

In past decades Greek leftist extremists have often targeted American personnel and institutions that included the assassination of the CIA station chief in Athens. The most notorious group was November 17, whose chief leaders are in jail serving life sentences.