Smoke rises over buildings during a crackdown by Hamas security forces on the Fatah-linked Hilles clan Saturday in Gaza City. Hamas forces on Saturday battled Fatah gunmen in a crowded Gaza City neighborhood, leaving at least nine dead and more than 80 wounded.

Gaza City, Gaza Strip ? Hamas forces battled Fatah-linked fighters with mortars and machine guns in a crowded Gaza neighborhood Saturday, leaving at least nine dead in the worst Palestinian infighting in nine months.

About 88 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 responsible for 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 non-violent 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 fled to Israel later in the day, Israeli military officials confirmed.

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.

Senior Hamas official Siyad Siam said those arrested included men allegedly involved in last week’s attack. Hamas forces found explosives like those used in the bombing, as well as machine guns and other weapons, Siam told a press conference in Gaza City late Saturday.

“We are sending a message that no one is above the law and that no family is above the law,” Siam said. “Gaza will enjoy peace and security.”