GAZA CITY, Gaza Strip -- Hamas forces battled Fatah-linked fighters with mortars and machine guns in a crowded Gaza neighborhood Saturday, leaving at least four dead in the worst Palestinian infighting in nine months.
About 80 people were injured, 12 of them children, hospital officials said.
Loud explosions and gunfire could be heard throughout the day in the Gaza City neighborhood of Shijaiyeh, a stronghold of the Fatah-allied Hilles clan. Hamas accuses the clan of hiding suspects behind a car bombing last week that killed five activists of the Islamic militant group.
Hamas and the largely secular, Western-backed Fatah have waged a violent struggle for control of Gaza for years. But there have been few signs of Fatah resistance since Hamas seized control of the strip in June 2007.
Relations between the factions deteriorated sharply last week after the car bombing that killed Hamas militants in Gaza and each side has been cracking down on political opponents with growing intensity. Hamas in Gaza and Fatah loyalists of Palestinian President Mahmoud Abbas who control the West Bank have carried out mass arrests.
In the West Bank, Abbas' troops enforced a new ban on public assembly and expanded their arrest sweep beyond Hamas. Club-wielding security men arrested and beat dozens of supporters of a nonviolent Islamic group.
The Gaza clashes began when Hamas raided Shijaiyeh under heavy morning fog. Security forces stormed several high-rise buildings and rounded up rooftop snipers, gunmen and wounded fighters, said Islam Shahwan, a Hamas police spokesman.
Heavy battles with mortars and machine guns ensued. Three Hamas policemen and a Hilles member were killed, hospital officials said.
It was the deadliest internal Palestinian fighting since November when Hamas police killed seven people in a Fatah-organized memorial rally for the late Yasser Arafat.
Ahmed Hilles, a clan leader and Fatah official, said Hamas police cut off electricity as they launched the raid. He explained why the clan fought back.
"You have to decide: Either be trampled under Hamas' shoes, or stand in dignity," he told The Associated Press by telephone, with gunshots crackling in the background. Hilles apparently fled to Israel later in the day.
By Saturday afternoon, Hamas police had seized control of Shijaiyeh, home to some 100,000 people. They deployed hundreds of police who went house to house in search of weapons and suspects. In all, more than 50 people were arrested, including some who had tried to flee disguised as women, Hamas said.
Hamas also fired several mortar shells toward the nearby border with Israel, apparently in an attempt to prevent fugitives from getting away.
More than two dozen members of the Hilles clan who fled the fighting were allowed through a Gaza crossing into Israel, Israeli military officials said. They spoke on condition of anonymity because no official announcement was made.
In the West Bank, security forces armed with clubs arrested and beat dozens of supporters of a non-violent Islamic group, the Liberation Party, and broke up their rally in downtown Ramallah. An AP Television News cameraman was prevented by Abbas' security forces from filming the beatings.
The pan-Islamic Liberation Party has sharply criticized the moderate Fatah leadership but says it espouses non-violent change. In the past, members of the movement were able to march in the West Bank without hindrance.
However, demonstrations in recent days have been broken up by Abbas' security forces, and one senior security official said there is growing fear Hamas is using the Liberation Party as a front in the West Bank.
Since Thursday, dozens of Liberation Party members have been arrested, said its spokesman, Baher Saleh.
Deeb al-Ali, chief of the national security forces in the West Bank, said all political gatherings were banned because of the growing tensions with Hamas.
"We have to stop rallies and marches or anything that leads to mass gatherings," he said.
Abbas' troops put on a show of force in Ramallah, marching in formation through the center.
Amir Qimari, 25, a food company employee, watched the military display with dismay.
"This became an oppressive and non-democratic government," he said of the Western-backed Abbas and his West Bank prime minister, Salam Fayyad. "What they say Hamas is doing in Gaza, they are doing here."
Security forces also patrolled the halls of Ramallah's hospital where some of those injured in the rally that was broken up were being treated. The forces prevented reporters from speaking to the injured.