TRIKALA, Greece >> At least eleven inmates have escaped from a prison in central Greece after gunmen brazenly attacked the site with grenades and automatic weapons, kicking off a nightlong standoff between police and prisoners.

A senior police official told the Associated Press on Saturday that 11 inmates were missing after the gun battle and standoff, which ended at dawn when police special forces entered the prison. He spoke on condition of anonymity because an official announcement was still pending.

The incident occurred near the town of Trikala, in central Greece. As many as six gunmen attacked the prison after driving up to the site in a van and pickup truck, according to officials. Two guards were injured.

Last month, guards foiled a breakout attempt by four prisoners who tried to escape by helicopter.