Egyptian security officials say Nobel Peace laureate Mohamed ElBaradei is under house arrest, the AP reported. Police stationed outside his suburban Cairo home told him he cannot leave the house after he joined tens of thousands of protesters in the capital Friday.

Earlier, police used water cannons against Mr. ElBaradei and his supporters as they joined the latest wave of protests after Friday noon prayers. Police also used batons to beat some of Mr. ElBaradei's supporters, who surrounded him to protect him.

Mr....