The United States, Russia, the EU and the United Nations were to have a ministerial level telephone conference on the crisis, while Arab foreign ministers gathered in Cairo for talks.

Egypt recalled its diplomatic and security delegations to the Gaza Strip.

"The presidency of the European Union condemns in the strongest terms the violent seizure of power by Hamas militia in the Gaza Strip," Martin Jaeger, German foreign ministry spokesman, said on behalf of the EU leadership.

"We condemn the killing of innocent civilians and legitimate security forces," the spokesman said.

Hamas fighters were in full control of the Gaza Strip on Friday, creating an Islamic enclave on Israel's doorstep and further clouding prospects for peace after routing their secular Fatah rivals in days of vicious gunbattles.

The radical Islamist group -- branded a terror outfit by Israel and the West -- overran the territory hours after Abbas sacked the government and declared a state of emergency in a bid to avert all-out civil war.

Jaeger joined the United States in backing Abbas, insisting that his decision to dismiss the three-month-old Hamas-Fatah unity government was "in accordance with the Palestinian constitution." Germany holds the EU presidency until the end of the month.

British Foreign Secretary Margaret Beckett stressed it would be wrong for Hamas to benefit from its seizure of power in Gaza.

"The notion that somehow mounting a coup d'etat is something that should be rewarded by the international community seems to me to be completely bizarre," she said.