Egypt's Salafist Al-Nur party said on Monday that it had withdrawn from talks on the formation of a new government in response to the killing of protesters calling for ousted president Mohamed Morsi to be reinstated.
"We have decided to withdraw immediately from all negotiations in response to the massacre outside the Republican Guard" headquarters, Al-Nur spokesman Nadder Bakkar said on Twitter.
The ultra-conservative Islamist Al-Nur, which won almost a quarter of votes in a 2011 parliamentary election, had given its support to the army's overthrow last week of Morsi, of the larger Muslim Brotherhood.
But it already voiced reservations about the transition plans of the military's chosen caretaker president, top judge Adly Mansour.
His plans to tap Nobel Peace laureate Mohamed ElBaradei, an outspoken liberal opponent of the Brotherhood, as interim premier ran into strong opposition from Al-Nur.
Mansour aides said before the fatal shootings that he was poised to announce his choice of premier following protracted negotiations with the Salafists and other groups.