President Mahmoud Abbas will dissolve the Palestinian Authority's government Thursday after fighting between rival parties Hamas and Fatah consumed the Gaza Strip and was expected to call for a state of emergency, sources close to Abbas confirmed to FOX News.

Abbas also fired Prime Minister Ismail Haniyeh of Hamas, dismantled the Hamas-Fatah coalition and said he would form a new government.

Abbas is also considering early elections at some stage, said his aide, Tayeb Abdel Rahim, in a news conference. Abdel Rahim said Abbas may "return to the people" when circumstances allow.

Other aides had said Abbas was also planning to call for the deployment of a multi-national force. However, Abdel Rahim made no mention of that in the news conference.

Abbas considers the Hamas fighters who have seized control of most of the Fatah-allied security headquarters in Gaza to be an "outlaw militia," Abdel Rahim said.

Hamas fighters took control from three of the rival Fatah movement's most important security command centers in the Gaza Strip, and witnesses said the victors dragged vanquished gunmen into the street and shot them to death execution-style.

Hamas has taken control of the Fatah-run National Security headquarters in Gaza City, the Islamic group claimed Thursday evening.

Earlier, Hamas forces took over the other main Fatah-linked security headquarters, in its steady takeover of important installations in the seaside territory.

Hamas also seized control of Rafah in the south, Gaza's third-largest city, according to witnesses and security officials. It was the second main Gaza city to fall to the militants, who captured nearby Khan Younis on Wednesday.

Hamas captured the Preventive Security headquarters and the intelligence services building in Gaza City, major advances in the Islamic group's attempts to take over Gaza.

• Reporter's Notebook: Hamas Versus Fatah — a Civil War Has Begun

After the rout at the security headquarters, some of the Hamas fighters kneeled outside, touching their foreheads to the ground in prayer. Others led Fatah gunmen out of the building, some shirtless or in their underwear, holding their arms in the air. Several of the Fatah men flinched as the crack of gunfire split the air.

A witness, who identified himself only as Amjad, said men were killed as their wives and children watched.

"They are executing them one by one," said Amjad, who lives in a building that overlooks the Preventive Security complex. "They are carrying one of them on their shoulders, putting him on a sand dune, turning him around and shooting," he said by telephone.

The killers ignored appeals from residents to spare the men's lives, said Amjad, who declined to give his full name, fearing reprisal.

Preventive Security is an especially despised target of Hamas because the agency carried out bloody crackdowns against the Islamic group in the 1990s.

PHOTOS: Hamas, Fatah Battle in Gaza Streets

Fatah officials said Hamas shot and killed seven of its fighters outside the Preventive Security building. A doctor at Shifa Hospital said he examined two bodies that had been shot in the head at close range. The officials and the doctor spoke on condition of anonymity for fear of reprisals.

Militants and civilians looted the compound, hauling out computers, documents, office equipment, furniture and TVs.

The moderate President Mahmoud Abbas of Fatah, for the first time in five days of fierce fighting, ordered his elite presidential guard to strike back. But his forces were crumbling fast under the onslaught by the better-armed and better-disciplined Islamic fighters.

In all, 14 fighters and civilians were killed and 80 wounded in the battle for the Preventive Security complex, bringing the day's death toll to 25, hospital and security officials said. About 90 people, mostly fighters but also women and children, have been killed since a spike in violence Sunday sent Gaza into civil war.

The two factions have warred sporadically since Hamas took power from Fatah last year, but never with such intensity. Hamas reluctantly brought Fatah into the coalition in March to quell an earlier round of violence, but the uneasy partnership began crumbling last month over control of the powerful security forces.

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Hamas had been tightening its grip on the Preventive Security complex for three days, stepping up its assault late Wednesday with a barrage of bullets, grenades, mortar rounds and land mines that continued until the compound fell. Electricity and telephone lines were cut, and roads leading to the complex were blocked. Hamas claimed it confiscated two cars filled with arms.

The Palestine Liberation Organization's top body recommended that Abbas declare a state of emergency and dismantle Fatah's governing coalition with Hamas. Abbas said he would review the recommendations and decide later Thursday, said an aide, Nabil Amr.

"We are telling our people that the past era has ended and will not return," Islam Shahawan, a spokesman for Hamas' militia, told Hamas radio. "The era of justice and Islamic rule have arrived."

Sami Abu Zuhri, a Hamas spokesman, heralded what he called "Gaza's second liberation," after Israel's 2005 evacuation of the coastal strip.

Israel was watching the carnage closely, concerned the clashes might spawn attacks on its southern border. Defense Minister Amir Peretz told a weekly meeting of security officials that Israel would not allow the violence to spread to attacks on southern Israel, meeting participants said.

White House press secretary Tony Snow called the situation "a source of profound concern" that is being monitored by Washington. He said Hamas has expanded its "acts of terror" to target the Palestinian people themselves.

"We are keeping a very close watch," he said. "It's certainly not a situation we like."

The European Union said it suspended humanitarian aid projects in Gaza, citing the escalating violence there.

The head of the Arab League, Amr Moussa, warned of a "disastrous outcome" if the bloody infighting continues and called for an immediate cease-fire.

Hamas, meanwhile, had its sights on two other key command centers in Gaza City.

In a broadcast on Hamas radio, the Islamic fighters demanded that Fatah surrender the National Security compound by midafternoon. Light clashes were under way there when the ultimatum was delivered.

RPGs were fired toward Abbas' Gaza compound, provoking return fire from his presidential guard. For the first time since the fighting began, Abbas ordered his guard to go on the offensive against Hamas at the compound, and not simply maintain a defensive posture, an aide said. He spoke on condition of anonymity because the situation was fluid.

Hamas fighters fired dozens of RPGs at the intelligence services building in Gaza City. When they captured it, Hamas television broadcast pictures of the fighters raising the group's green Islamic flag on the roof.

In Rafah, Hamas took over the Preventive Security building, according to witnesses and Col. Nasser Khaldi, a senior police official.

"I can see the Preventive Security building in front of me. Hamas has raised its green flags over it," said a civilian resident, who identified himself only as Raed. He said men carried away equipment from inside and the Fatah-allied security men ran away.

Near Rafah, Hamas officials said an Israeli tank shell struck a group of children from the same family riding in a car, and hospital workers said five were killed. The Israeli army denied its forces fired in the area.

Gaza hospitals were operating without water, electricity and blood.

Even holed up inside their homes, Gazans weren't able to escape the fighting. Moean Hammad, 34, said life had become a nightmare at his high-rise building near the Preventive Security headquarters, where Fatah forces on the rooftop were battling Hamas fighters.

"We spent our night in the hallway outside the apartment because the building came under crossfire," Hammad said. "We haven't had electricity for two days, and all we can hear is shooting and powerful, earthshaking explosions.

"The world is watching us dying and doing nothing to help. God help us, we feel like we are in a real-life horror movie," he said.

Fatah has threatened to carry the fighting to the West Bank, where Hamas is weak. There have been sporadic battles in the West Bank this week, and on Thursday, Fatah went across the territory rounding up Hamas fighters in an effort to assert control.

The violence has exposed the depths of the disarray in Fatah's ranks since Hamas ended Fatah's 40-year dominion of Palestinian politics last year.

Fatah has asked Israeli permission to bring in more arms and armored vehicles, but Tzahi Hanegbi, chairman of the Israeli parliament's Foreign Affairs and Defense Committee, told Army Radio that arming Fatah would be "insane" because the weapons would fall into Hamas hands.

He said Israel was considering backing Fatah forces in the West Bank, but did not elaborate.

The Associated Press contributed to this report.