Security remained tight around the main Coptic cathedral in Egypt's capital Cairo on Monday, days after sectarian violence left several people dead.
Two more deaths were reported on Monday as clashes between Coptic Christians and Muslims continued.
A 21-year-old Muslim man, named only as Mohamed, died of a fractured skull in hospital, a security source said.
His death followed fighting between local Muslims and Copts who had been attending a funeral for four Christians shot dead in a town near Cairo.
The health ministry said at least 90 people, including 11 policemen, were wounded around St Mark's Cathedral, seat of the Coptic pope.
The violence is the worst sectarian unrest since the fall of President Hosni Mubarak in 2011.
Separately, the state news agency MENA said one person was killed and 14 wounded in fresh clashes on Sunday night in the town of El Khusus, north of Cairo, where the latest wave of sectarian strife began on Friday.
Hisham Kandil, Egypt's prime minister, said the government was taking all measures to protect the safety of Egyptians of all faiths.
Kandil promised to bring to justice the perpetrators of sectarian attacks and to crack down on unlicenced weapons.
He also spoke to the heads of the Coptic church and of the Islamic al-Azhar institution to discuss ways to resolve the crisis, a cabinet statement said.
The violence erupted as Egypt is negotiating with a visiting International Monetary Fund delegation for a loan of at least $4.8bn to ease a deepening economic crisis aggravated by political and sectarian turmoil.
The crisis has hit investment and tourism in the Middle East's most populous nation.
Muslim and Christian religious leaders appeared together on late-night television to call for calm and national unity.
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Witnesses accused the police of standing by as the Copts were attacked and of firing teargas at mourners in the compound as they emerged from the cathedral under a hail of rocks.
A statement posted on the interior ministry's website blamed Christians for starting the trouble by vandalising several cars.
President Mohamed Morsi telephoned Coptic Orthodox Pope Tawadros II on Sunday evening to condemn the violence, telling him that "any attack on the cathedral is like an attack on me personally".
In a condolence message to the families of the victims, Tawadros said on Monday: "Heavenly justice will be spoken at the appropriate time."