Israel killed Abdel Aziz Rantissi (search) in a missile strike on his car on Saturday, part of its declared campaign to wipe out the Islamic militant group's leadership before Israel's planned withdrawal from the Gaza Strip. Two of Rantissi's bodyguards were also killed in the attack.

Palestinians demonstrated Sunday throughout the Gaza Strip and West Bank calling for attacks to retaliate for the assassination. In the West Bank city of Ramallah (search), Israeli soldiers shot and killed a 14-year-old Palestinian boy in a riot against the killing, hospital officials said.

Tens of thousands of Palestinians filled the streets of Gaza City on Sunday in Rantissi's funeral procession. Hamas supporters chanting "God is great" and "revenge, revenge," threw flowers at the three men's stretchers as they carried them from the hospital.

About 200 armed Hamas militants lined both sides of the road and gave the bodies a military salute as they approached a large blue and green mourning tent set up outside Rantissi's house. Armed men fired into the air and many in the gathered crowd raised their fists in anger.

Green Hamas flags and black mourning flags hung from nearby homes.

"Hamas will move ahead and will continue the resistance march," said local Hamas leader Ahmad Sahar, a friend of Rantissi's.

Hamas posted a statement on its Web site pledging "100 unique retaliations" that will shake Israel. It said it had declared a state of emergency in the West Bank and Gaza Strip until revenge was complete.

"Yesterday they said that they killed Rantissi to weaken Hamas. They are dreaming. Every time a martyr falls, Hamas is strengthened," Ismail Haniyeh, a Hamas leader, told more than 70,000 mourners gathered at the city's largest mosque for the funeral. "Hamas might have a crisis at hand after losing its leaders, but it will not be defeated."

Rantissi was killed less than a month after Israel assassinated Hamas spiritual leader Sheik Ahmed Yassin. The group's Damascus-based leader Khaled Mashaal reportedly instructed the organization to keep the name of its new Gaza leader secret.

Israel has targeted Hamas and its leaders in advance of Prime Minister Ariel Sharon's proposed withdrawal from all of the Gaza Strip and a few West Bank settlements.

Sharon vowed to continue hunting down Hamas leaders.

"This policy of making an effort on the one hand to advance a political process and on the other hand to hit the terror organizations and their leaders will continue," Sharon said at the start of his weekly Cabinet meeting Sunday.

Sharon returned from Washington Friday with strong U.S. backing for his plan, as well as unprecedented U.S. support for Israel to hold on to parts of the West Bank under a final peace deal.

Sharon has called for a May 2 referendum on his plan in his hard-line Likud Party, and polls show the proposal garnering a slim majority of the party's 200,000 voters.

Two key Israeli Cabinet ministers, Finance Minister Benjamin Netanyahu and Education Minister Limor Livnat, decided Sunday to back the plan, giving Sharon a Cabinet majority and the support of influential Likud members.

Vice Premier Ehud Olmert denied there was a connection between the referendum and Rantisi's assassination. But the killing underscored Israel's commitment to continue fighting terrorism and hunting down militant leaders even after a pullout, he said.

Israeli Cabinet minister Gideon Ezra said Mashaal — the overall Hamas leader who Israel tried unsuccessfully to kill in the past — was also marked for death.

"The fate of Khaled Mashaal is the fate of Rantissi. The minute we have the operational opportunity we will do this," Ezra said.

The Bush administration declined to criticize Rantissi's killing, saying instead that Israel has the right to defend itself from terrorist attacks and urging Palestinians to use restraint in responding.

"The United States strongly urges Israel to consider carefully the consequences of its actions," White House press secretary Scott McClellan said

Arab officials and Muslim leaders called the assassination "state terrorism" that proved Israel was intent on sabotaging peace hopes and suggested American support for such killings, an accusation Israel and the United States denied. Earlier in the week, a taped message attributed to Osama bin Laden vowed revenge against America for the Israeli killing of Yassin.

Israeli security forces went on high alert after Rantisi was killed, fearing reprisal bombings. Palestinian leader Yasser Arafat condemned the killing as a "brutal assassination."

Black smoke from burning tires billowed over Gaza and fresh graffiti promising fierce revenge decorated the walls of the crowded coastal strip. Streets remained empty and stores shuttered as Gazans marked the first of a three-day mourning period for Rantisi. Children stayed home from school.

In the West Bank, the Palestinian Authority instructed schools to devote the first half-hour of lessons to Quran readings in a sign of mourning. Flags were flown at half staff at Arafat's Ramallah headquarters.

In the city of Nablus, crowds hung up effigies of Israeli Prime Minister Ariel Sharon and U.S. President George W. Bush, shot them and then burned them as they chanted "revenge, revenge."

Rantissi's car was hit by two missiles Saturday evening about a block from his house in the Sheik Radwan neighborhood of Gaza City.

Rantissi ran about 15 meters (yards) from the car, collapsed and lost consciousness, Ghazal said. The Hamas leader, his body pocked with bloody wounds and blood streaming from his head and neck, was rushed to the hospital and into emergency surgery. He died five minutes after arriving.

Israeli officials accused Rantissi of planning a large attack on Israel to solidify his leadership of Hamas and to retaliate for Yassin's killing. Hamas is responsible for most of the 112 homicide bombings that have killed 465 people on the Israeli side during 3 1/2 years of violence.

Israel has killed more than 150 militants in targeted raids since fighting broke out in September 2000, according to Palestinian medical officials, though that total includes militants killed resisting arrest.

Also Sunday, the Israeli army killed a Palestinian armed with a rifle who tried to infiltrate a Jewish settlement in Gaza. Hospital officials identified the man as Nael Mohammad Omar, a 22-year-old Islamic Jihad member.