Egypt's military rulers have held emergency talks with Christian leaders after the worst violence since February's revolution left 26 people dead and 300 injured - and raised grave doubts about the country's democratic transition.
The Coptic church called on followers to fast and pray for three days from Tuesday to mourn Christians killed in clashes with security forces on Sunday, now the subject of an investigation ordered by the ruling Supreme Council of the Armed Forces (Scaf), led by field marshal Mohammed Hussein Tantawi.
Issam Sharaf, the interim prime minister, warned of a "despicable conspiracy" against Egypt and called for unity.
Video clips of the incident showed military vehicles ploughing through crowds of demonstrators so that several were crushed to death.
It was the worst violence since Hosni Mubarak was ousted on February 11. The Copts insist they were marching peacefully when thugs attacked them, drawing in the military police who used what activists described as unnecessary force.
With tensions running high, security was stepped up in central Cairo, with additional troops deployed outside parliament and the cabinet building.
{{/usCountry}}With tensions running high, security was stepped up in central Cairo, with additional troops deployed outside parliament and the cabinet building.
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