Thousands of Egyptian riot police beat pro-democracy activists Thursday, chasing and dragging them through the streets to break up a demonstration in support of judges who blew the whistle on election fraud.

The violence appeared to signal a tough new zero-tolerance stance by the government toward protests demanding reform and expressing discontent that President Hosni Mubarak has backed off promises of democratic change.

The State Department said it was “deeply concerned” about the police assault on protesters and would raise the matter with the government.

The protests were called to support two judges from Egypt’s highest court who became heroes of the democracy movement after they went public with allegations of fraud during parliamentary elections last year.

The judges, Hisham el-Bastiwisy and Mahmoud Mekki, have been ordered before a court panel for possible disciplinary action. But they boycotted their hearing Thursday to protest the treatment of the demonstrators and the session was postponed.