GAZA At least 25 Palestinians were killed on Wednesday as President Mahmoud Abbas's secular Fatah faction and Hamas battled for control of Gaza and Israel launched a deadly round of air strikes against the Islamists.
Palestinian officials said the widening hostilities could bring down a two-month-old unity government formed between Hamas and Fatah. Some Palestinians see this leading to all-out civil war and the end of the Palestinian Authority.
Terrified Gaza residents hid indoors as masked gunmen fought running battles street-to-street, killing 20 people -- five of them even after the two sides declared a ceasefire at dusk. In one panicked call to a radio station, a woman urged Palestinian leaders to act, pleading: "Do not leave us to die here."
Israel's biggest air strike razed a building used by Hamas's Executive Force in the south Gaza town of Rafah, killing four militants. Israel said the attack was not connected to internal clashes that have killed at least 44 people since Friday.
A later air strike in northern Gaza killed another Hamas militant and wounded two other Palestinians, residents said.
While battles raged throughout the Gaza Strip, militants have fired rockets at southern Israel, causing injuries but no deaths, in an apparent attempt to draw Israel into the fighting.
Israel said the air strikes, the deadliest since a November truce in Gaza was declared, targeted a Rafah command centre used by Hamas to plan attacks and a rocket crew that had just fired into the Jewish state.
The Executive Force, which has taken a lead in fighting with Fatah, denied the Rafah building was used to plan rocket attacks and said the air strikes proved Israel was taking sides.
Foreign Minister Tzipi Livni said Israel may step up military strikes in the Gaza Strip in response to a surge of Palestinian cross-border rocket salvoes.
"Until now, we have demonstrated restraint, but this situation is not a tolerable situation," Livni told reporters after security consultations with Prime Minister Ehud Olmert and Defence Minister Amir Peretz.
Israel faces a delicate balancing act. It is under domestic pressure to stop the rockets and also wants Fatah to deal a blow to Hamas, the party of Prime Minister Ismail Haniyeh; it agreed to let 450 Fatah troops into Gaza from Egypt on Tuesday.
But overt Israeli assistance for Fatah could backfire if Hamas is able to paint Abbas as an ally of the Jewish state, which many Palestinians see as their real enemy. Pro-Hamas media have already begun accusing Abbas of lining up with Israel.
"We will not intervene in the war itself but if Mr. Abbas will request specific help, we will supply (it)," Israeli Vice Premier Shimon Peres told reporters during a visit to Estonia.
CEASEFIRE BLOWN AWAY
Hamas and Fatah declared a ceasefire at 8 p.m.(1700 GMT). But five armed men died in later clashes. Fierce gunfire and explosions were still heard across the cramped coastal enclave.
Earlier in the day, Hamas gunmen stormed the home of Abbas's top security chief, Rashid Abu Shbak, and fired mortars at the compound Abbas uses on his visits to Gaza from his main base in the West Bank. Later shooting near Haniyeh's home was labelled "accidental" by pro-Hamas officials after one had initially described it as an attack in which no one had been hurt.
At least 50 journalists were trapped in Gaza's main media centre. They said the building was surrounded by gunmen and some people inside had been injured.
Some Western officials say the government's collapse could allow Abbas to assert more control, leading to an end to a Western aid embargo ahead of possible early elections.
A Palestinian official said Abbas cancelled a trip to Jordan and planned to travel to Gaza on Thursday to try to restore calm. Several Fatah leaders have urged him to declare a state of emergency to allow him to rule by decree for a limited period.
Western powers expressed alarm at spiralling anarchy that underscored the lack of peace talks with Israel. "It's clear that everyone needs to work with President Abbas to calm the situation down," U.S. State Department spokesman Tom Casey said.
In Wednesday's deadliest single attack, five detained Hamas gunmen and two Fatah escorts were killed when their vehicle, travelling to a detention centre, came under fire.
Security officials said the vehicle was attacked by Hamas fighters, but a spokesman for Hamas's Executive Force said they were "executed ... in cold blood" by Fatah. Fatah said at least nine of its members were killed in Wednesday's fighting.
(Additional reporting by Dan Williams, Ori Lewis, Jeffrey Heller, Adam Entous and Alastair Macdonald in Jerusalem; and Mohammed Assadi in Ramallah)