ATHENS - Gunshots were fired at the German ambassador's residence in Athens early on Monday, but caused no injuries or damage, police said.

At least four shots hit the outside metal gate of the residence, which lies behind a security wall on a busy street in a northern suburb of the Greek capital, police said. Investigators have collected 15 spent bullet cases so far.

The police sources said two attackers on foot were involved in the attack, which occurred at about 3.40 am (0140 GMT),

Greek Prime Minister Antonis Samaras spoke to the German ambassador to Athens, Wolfgang Dold, after the incident, a police statement said.

Anti-German rhetoric has become common among Greek opposition politicians and anti-bailout groups since the country's international financial bailout in 2010, due to the harsh austerity policies that accompanied it.

Germany is the biggest single contributing nation to 240-billion euro financial rescue and has been pushing Athens for painful budget cuts and reforms to fix its finances.

The residence was the target of an attack in 1999, when members of the now dismantled extremist group November 17 fired a rocket that hit its roof.