Cairo, Egypt - The United States has voiced concern about violence that killed 25 people in Egypt, mainly Coptic Christians, as anger mounts in the Arab country against its ruling military.
US Secretary of State Hillary Clinton phoned Egyptian Foreign Minister Mohammed Kamel Amr over the clashes in which the army and thugs attacked a demonstration by Copts in Cairo on Sunday.
In the call, Clinton conveyed "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."
She also expressed "deep concern about the violence" and condolences for those killed and injured, the State Department said late on Tuesday.
Egypt's deputy prime minister Hazem al-Beblawi announced earlier that day that he was resigning, saying that despite having no direct involvement in the clashes, the government ultimately bore responsibility for what happened.
"The current circumstances are very difficult and require a new and different way of thinking and working," Beblawi was quoted as saying by the official MENA news agency.
Field Marshal Hussein Tantawi, Egypt's military ruler, rejected Beblawi's resignation, government spokesman Mohammed Hegazi said without elaborating, MENA later reported.
On Sunday, 25 people were killed and more than 300 injured when a protest by Copts was attacked by the army and thugs, sparking furious condemnation of the leadership's handling of the transition from the rule of ousted president Hosni Mubarak.
Military prosecutors said they have remanded 28 people in custody -- both Muslims and Christians -- for 15 days pending investigations, MENA reported.
The Supreme Council of the Armed Forces (SCAF), which took power when Mubarak was ousted in February, had tasked Prime Minister Essam Sharaf's government immediately to form a fact-finding panel to investigate the clashes.
The UN human rights office has urged Egypt to ensure any probes are conducted in an impartial and independent manner.
Rupert Colville, spokesman for the UN High Commissioner for Human Rights, urged the authorities "to ensure the impartiality and independence of any investigation undertaken into the incident."
Political and religious leaders have held crisis talks amid fears of widespread sectarian unrest threatening an already fragile transition.
On Sunday, the Copts had been protesting against a recent attack on a renovated village church in the southern province of Aswan.
State television accused the demonstrators of firing shots that killed three soldiers, prompting fights between Christians and Muslims.
But furious Copts said the security forces attacked the demonstrators, driving vehicles into the crowd and crushing several people.
New York-based rights group Human Rights Watch has called for a "prompt, thorough and impartial" investigation, which "should specifically address the killing of at least 17 Coptic Christian demonstrators who appear to have been run over by military vehicles."
"It should also examine the role of the military and police officers in the violence," HRW said in a statement.
Copts complain of systematic discrimination, but since Mubarak's fall tensions have also mounted between the military -- initially hailed for not siding with Mubarak -- and groups which spearheaded the revolt.
Egypt's Coptic Orthodox Church led by Pope Shenuda III accused "infiltrators" of triggering the street battle on the Nile waterfront, while the country's top Muslim official, Grand Imam Ahmed al-Tayyeb, urged the cabinet swiftly to issue a unified law on building places of worship.
The cabinet vowed this week to look into amending religious laws which would give Copts more guarantees to freedom of worship.
But after months of tensions, unrest and clashes, some say the measure is too little too late.
On Tuesday, leading independent daily Al-Masry Al-Youm called for the resignation of the prime minister.
"The state has lost its stature, the regime is on the verge of collapse, and Sharaf's government has run out of credit. All that is left to say is Sharaf, resign," it said in a front page editorial.
The liberal Wafd party's mouthpiece echoed the view: "After what has happened, we can say that he cannot serve as a prime minister and he must leave his post."
International calls for restraint poured in, as the Arab world's most populous nation teetered on the edge of widespread unrest, and activists feared their revolution was crumbling.
Saudi Arabia urged Egypt to exercise restraint. The White House said President Barack Obama was "deeply concerned," and a "deeply saddened", while UN chief Ban Ki-moon urged the military to defend "all faiths."
Amnesty International said the military "must urgently explain how a protest against religious discrimination turned into a bloodbath."
The International Federation for Human Rights condemned the "use of excessive force," with IFHR president Souhayr Belhassen saying this raised the question about the SCAF's ability to lead the transition.