GAZA CITY, June 12: Hamas fighters besieged two Fatah security headquarters with guns and rocket launchers on Tuesday as deadly clashes threatened to topple the government and drive Gaza closer to civil war.

Gunmen from the Islamist movement attacked two seats of the Fatah loyalist national security -- the main Palestinian security force -- in Gaza City and Jabaliya, sparking heavy clashes with those holed up inside.

Security officials and witnesses said Hamas gunmen quickly abandoned the fight at the Gaza City base when defenders repelled their attempts to storm it, but that fighting was continuing at the larger base in Jabaliya.

Hamas's Ezzedine al-Qassam Brigades unilaterally declared “the northern Gaza Strip a closed military zone” under its control and called on members of the mainstream Fatah loyalist security forces to stay at home.

Dozens of security officers loyal to Fatah laid siege to the headquarters of Hamas's Al-Aqsa television before withdrawing after Hamas fighters turned up and ripped gunfire through three of their vehicles, witnesses said.

Earlier mortar shells slammed into prime minister Ismail Haniya's home and the seafront compound of president Mahmud Abbas in the latest bout of fighting that killed two people on Tuesday, bringing the death toll to 18 in 24 hours.

The bitter conflict, in which hospitals have become battlegrounds, threatens to sink the Hamas-Fatah coalition that took office less than three months ago in a bid to halt the feuding that has killed nearly 180 people since December.

“All the information and all the facts point to a faction, to which political and military leaders of Hamas belong, who are plotting a coup against Palestinian legitimacy,” the presidency said.

It charged that the Hamas leaders in question were “pushing the homeland towards the throes of a dreadful civil war” and issued a plea on behalf of Abbas for an immediate ceasefire and serious dialogue.

Fatah announced that the party's central committee was examining whether it should remain in government and slammed Hamas for “looking to annihilate the Palestinian Authority and create a republic of hate and death” in Gaza.

Haniya's office weighed in with a statement charging that “parties linked to enemies tried to bring down the national unity government militarily.” In New York, UN spokeswoman Michele Montas said in a statement that Secretary General Ban Ki-moon “is deeply concerned at the resurgence of violence in Gaza,” which threatens “the future of the Palestinian government and Authority.” Ban “calls for the immediate cessation of all intra-Palestinian violence, including attacks against the Palestinian Authority and its institutions ... and for all parties to give their full support to the efforts of Palestinian President Mahmoud Abbas to restore law and order,” the statement added.

Defying the latest Egyptian-brokered ceasefire, Gaza plunged into renewed violence five days ago, just weeks after a bout of strife left 54 people killed when tempers boiled over on how to implement a flagship government security plan.

Palestinian civilians cowered in their homes as shooting and explosions reverberated through the streets outside.

“Since early morning we have heard explosions and shooting. We can't go and buy any food, we can't stand in front of the windows, all our children are in one bedroom. The situation is very bad,” said Adnan, a doctor in Gaza City.

The International Committee of the Red Cross and non-governmental organisation Physicians for Human Rights Israel condemned killing at hospitals after battles reported around medical facilites in Gaza City and to the north.—AFP