WASHINGTON — US Secretary of State Hillary Clinton voiced "deep concern" about deadly weekend violence that killed 25 people in Egypt, mainly Coptic Christians.

Clinton phoned top Egyptian diplomat Mohamed Kamel Amr to convey "the need for the Egyptian government to ensure that the fundamental rights of all Egyptians are respected, including the rights of religious freedom, peaceful assembly and the end of military trials for civilians, and that efforts be made to address sectarian tensions," the State Department said.

She also expressed "deep concern about the violence" and condolences for those killed and injured in the clashes.

Sunday's violent unrest came amid mounting anger at the ruling military and calls for the premier to quit.

Over 300 people were also injured in the clashes that saw a protest demonstration by Copts attacked by the army and thugs, sparking furious condemnation of the leadership's handling of the transition from Hosni Mubarak's rule.

The Supreme Council of the Armed Forces, which took power when Mubarak was ousted in February, tasked Prime Minister Essam Sharaf's government to immediately form a fact-finding panel to investigate the clashes.

Clinton lauded the decision to launch a "transparent and credible" probe but "stressed the importance of the investigation beginning immediately and holding accountable all responsible parties with full due process of law."

The UN human rights office has also urged Egypt to ensure that any probes are conducted in an impartial and independent manner.

Military prosecutors said they have remanded 28 people in custody -- both Muslims and Christians -- for 15 days pending investigations, according to the official MENA news agency.