Israel tried to kill the mastermind of the Hamas bombing campaign Thursday, firing two missiles from a helicopter into a car in crowded Gaza City and killing two bodyguards. Thirty-five bystanders were wounded but the fate of the Palestinian militant remained uncertain.

A senior Palestinian security official said Israel's target, 37-year-old Mohammed Deif, escaped with moderate injuries. Israeli police sources said the Israeli military told them Deif -- atop Israel's wanted list for years -- was killed. The military had no comment.

Hamas official Abdel Aziz Rantisi said Deif was not even in the car. But he said the group would avenge the attack nevertheless. "We will hit Tel Aviv. We will hit everywhere."

Hamas and the Palestinian Authority are rivals, possibly explaining the different versions of Deif's fate.

In a pre-dawn raid Friday, Israeli soldiers carrying out a house search shot and killed an armed 21-year-old Hamas militant in the West Bank city of Hebron, Palestinian witnesses and hospital officials said. The army declined immediate comment.

In other violence, four Palestinians -- including two gunmen, a civilian and a baby -- and one Israeli were reported killed. Israel maintained its stranglehold on Palestinian leader Yasser Arafat's headquarters in the West Bank town of Ramallah in defiance of Tuesday's U.N. Security Council resolution to end the siege.

Two helicopters appeared in the sky over Gaza just after 1:30 p.m., firing missiles that blew apart a green Mercedes sedan and sent a plume of white smoke over the Sheik Radwan neighborhood.

"Suddenly we heard the sound of a big explosion," said Mohammed Hajar, a hairdresser working in the area. "When I ran out, a second explosion took place."

Blood, body parts and shrapnel were strewn across a wide area and nearby windows were shattered. A large crowd, confused and angry, gathered as rescue workers led the wounded to ambulances.

One man leapt on a car and shouted, "God is great."

Hamas sources identified the two dead men as members of Hamas, Abdel Rahim Hamdan, 27, and Issa Abu Ajra, 29. Rantisi said they were Deif's bodyguards.

More than a dozen children were wounded in the attack, the latest in a series of assaults the Israeli military calls "targeted killings" of Palestinians.

The most controversial, a strike in Gaza that killed Hamas militant Salah Shehadeh, also killed nine children and five adult civilians.

In the past two years, at least 78 wanted Palestinians and 52 bystanders have been killed in such attacks, which the Palestinians deride as a policy of assassination. Human rights groups have condemned the policy.

"Today's attack is another example that shows clearly that the Israeli army doesn't care about the life of the innocent Palestinian victims," said Samieh Mouhsen of the Palestinian Society for the Protection of Human Rights. "It constitutes a policy of lawless disregard for the most fundamental human rights, the right to life."

At the United Nations, U.N. Secretary-General Kofi Annan deplored the Israeli attack on Gaza. A statement said Annan "calls on the government of Israel to halt such actions."

Israel says the targeted killings are its best means of preventing terror attacks, and accuses Arafat's Palestinian Authority of doing nothing against the radical groups and even encouraging them. Palestinians argue Israel's travel restrictions and military strikes have left their security services powerless.

Israelis accuse Deif of having a role in dozens of homicide attacks over the past six years. He survived an Israeli airstrike earlier this year.

When Israel killed Deif's mentor Yehiyeh Ayyash in 1996, Hamas responded with four homicide bombings that killed dozens of Israelis.

Israel has long pressed Palestinians to seize Deif, and accused Arafat of sheltering him. Hamas, however, often as been at odds with Arafat.

Palestinian officials arrested and held Deif for several months until December 2000. The Palestinians said he escaped. Israeli officials said his jailers set him free.

Late Thursday, about 3,000 Hamas supporters demonstrated near the site of the attack. Organizers said the purpose was to give thanks for Deif's safety.

In other developments:

-- Four Israelis, a mother and her three children -- one a month-old infant -- were wounded in a shooting attack on their car south of Hebron in the West Bank, Israeli police and rescue workers said. Earlier, a doctor said a 14-month-old Palestinian baby died in Hebron, apparently overcome by tear gas that Israeli soldiers fired into a market to re-impose a curfew; Israel's army confirmed its forces had fired two gas grenades but could not confirm that the baby died as a result.

-- Prime Minister Ariel Sharon was quoted as defending Israel's siege of Arafat's compound, where about 200 Arafat aides and members of the security forces have been confined to a few rooms since Sept. 19. In an interview published by the Jerusalem Post newspaper, he said some of those inside are "the biggest terrorists that exist." The assault on Arafat's headquarters came in response to a Tel Aviv bus bombing by Hamas that killed six people.

-- Terje Roed-Larsen, the chief U.N. envoy for the Middle East, warned Thursday that Israel's siege of Arafat is undermining reforms of the Palestinian Authority and could lead to anarchy that threatens both Israelis and Palestinians.

-- In the Gaza Strip, the Al Aqsa Martyrs Brigades, linked to Arafat's Fatah movement, claimed responsibility for an attempted infiltration into the Elei Sinai Jewish settlement early Thursday. One gunman was killed by soldiers, the army said.

-- In the West Bank town of Jenin, a 52-year-old civilian was shot dead when he opened his bedroom window during an Israeli military operation, the man's son said. The army admitted that the man was a civilian and expressed regret.

-- Elsewhere in the West Bank, a wanted Hamas militiaman opened fire Thursday at troops chasing him, killing an Israeli army officer before being shot dead by troops.