Police battled with anarchists late into the night following two marches protesting against US President Barack Obama's visit to Athens. Greek police estimated as many as 150 anarchists were involved in the clashes. They responded to rocks and Molotov cocktails with tear gas and stun grenades.<br/><br/>By late at night, police had confined the violence to the area of the Athens Polytechnic, a campus anarchists have used in the past as a safe haven from police, who are not allowed onto university grounds without a request from the Chancellor. Police said there were no injuries or damage to private property.