Egypt has tightened security after 10 people died in sectarian clashes in the Imbaba district of Cairo. United Nations Secretary General Ban Ki-moon said Wednesday that he was disturbed by clashes between Christian Copts and Muslims in Egypt, days after deadly violence in Cairo.Ban expressed concern that sectarian clashes could affect the recent progress towards democratic reform and a \"more free, just and harmonious Egypt.\"
\"I am disturbed by the recent violence between Muslims and Copts in Egypt after the prolonged display of national unity that led to the peaceful transition of power,\" the UN chief told journalists.
\"It is critical that the people of Egypt maintain that unity of purpose for .. their democratic aspirations,\" he added.
Egyptian pro-democracy activists have called for nationwide \"unity\" protests on Friday, including in the symbolic heart of rallies that brought down president Hosni Mubarak in February, Cairo\'s Tahrir Square.
\"The revolutions in Tunisia and Egypt represent one of the greatest opportunities to advance democracy and human rights in a generation,\" Ban said, calling it a \"once in a generation opportunity.\"
\"This opportunity is precious but at the same time fragile -- it must be nurtured and carefully handled by the people who created it,\" he added.
Egyptian authorities said on Monday they had captured the \"mastermind\" behind the clashes in Cairo\'s northwest neighbourhood of Imbaba that left at least six Muslims and four Christians dead and left a church ablaze.
The clashes in Imbaba occurred after Muslims attacked the Coptic church of Saint Mena to free a Christian woman they alleged was being held against her will because she wanted to convert to Islam.
The military council governing Egypt and the media have blamed recurring sectarian violence on a \"counter-revolution\" by old regime diehards.