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Twin Palestinian homicide bombings -- one at a bus stop crowded with soldiers near Tel Aviv, the second five hours later at a popular Jerusalem nightspot -- killed at least 15 Israelis and wounded and maimed dozens as the region grappled with a new wave of savage bloodletting.

Nobody claimed responsibility, but the Islamic militant group Hamas (search), which has carried out most of the roughly 100 homicide bombings against Israelis over the last three years, had been expected to avenge Israel's attempt on the life of its spiritual leader on Saturday.

Israel Radio reported that the two bombers were Hamas activists from Rantis village west of Ramallah in the West Bank. The Tel Aviv bombing killed eight Israelis and the Jerusalem bombing seven, one of whom died in a hospital early Wednesday.

In one Gaza neighborhood, Palestinians fired assault rifles in the air and about 100 took to the streets in celebration after the attack on the cafe. In the Bureij refugee camp in the central Gaza Strip (search), some Hamas supporters celebrated by distributing candies to the families of those killed in previous violence.

Israel's military has relentlessly targeted Hamas militants since the group claimed a homicide bombing last month that killed 22 people on a Jerusalem bus. Earlier Tuesday, Israeli troops in Hebron killed two Hamas members -- including the group's leader in the West Bank town -- and a 12-year-old bystander, and blew up a seven-story apartment building where the militants were hiding out.

The day's violence underscored the collapse of U.S.-backed peace efforts and came amid political uncertainty after the resignation of Palestinian Prime Minister Mahmoud Abbas (search).

An increasing number of Israeli officials were calling for the expulsion of Yasser Arafat (search), and expectations were mounting that Israel will step up military strikes and possibly invade the Gaza Strip -- which Israel has not yet reoccupied -- to root out the Hamas leadership.

The attacks came as Prime Minister Ariel Sharon (search) was away on a visit to India. Spokesman Raanan Gissin said he would shorten the visit by a day and return to Israel Wednesday.

Security was extremely tight throughout the country, especially in Jerusalem, in anticipation of a Hamas attack.

The first bombing came about 6 p.m., as soldiers were waiting for rides home outside the Tsrifin army base near the Tel Aviv suburb of Rishon Letzion.

Cpl. Eyal Schneider, 20, was walking toward the bus stop when he heard the explosion and saw a fireball. "People were running from the bus stop shouting 'bomb! bomb!"' he said.

Ambulances from nearby Assaf Harofeh hospital quickly lined up at the scene, rescue workers rushing to aid screaming victims.

"I saw the bodies, the body parts strewn around, heard the screams, and tried to help," said one witness, who gave his name only as Roy.

Police and hospital officials said eight were killed in addition to the bomber. Fifteen people were being treated at the hospital, all but one of them soldiers, spokeswoman Nurit Nehemia said. Others were treated for minor injuries and released. Hours later, the aluminum walls of the bus shelter remained splattered with blood.

Leaders of Hamas praised the attacks but stopped short of claiming responsibility. "This operation, whoever is behind it, is a natural reaction for the bloody aggression against our people," said Hamas spokesman Abdel Aziz Rantisi, who survived an Israeli attempt on his life in June.

Israeli government spokesman Avi Pazner said "the responsibility is shared between the organization that carried out the atrocity and the Palestinian Authority that did nothing to prevent it, and Israel will react accordingly."

Daniel Seaman, another government spokesman, said Israel will try to continue with the peace process. "But at the same time we will not allow our civilians to be murdered."

More than five hours later, about 11:20 p.m., another homicide bomber entered the Hillel Cafe, a popular bistro in the posh German colony neighborhood of Jerusalem.

Police said the bomber managed to get into the cafe even though two security guards were posted at the entrance -- one inside the door and one outside. Jerusalem police commander Mickey Levy told Israel Radio that one of the guards saw the bomber and tried to stop him, and that he then set off the bomb.

Seven Israelis died and more than 30 were wounded.

"I have a store next to the cafe. I arrived just a few moments after the blast. I saw things that just can't be described, there are no words," said a witness who identified himself only as Shavi.

The blast set off the siren alarms of dozens of parked cars nearby. Police were breaking windows of cars to check if they contain bombs as rescue workers led the wounded away on stretchers. A dazed, wounded man sat on the street, holding a bloody T-shirt to his head.

White House spokesman Scott McClellan, speaking outside a fund raiser for President Bush in Fort Lauderdale, Fla., called the bombings "vicious attacks" and condemned them in the "strongest possible terms."

McClellan said Bush remained committed to the "road map" peace plan, but he said the bombings "underscore the need to fight terrorism and the need to dismantle terrorist organizations and groups like Hamas."

State Department spokesman Richard Boucher emphasized "the urgency with which the Palestinian Authority needs to take immediate and effective steps to dismantle and disarm the terrorist capabilities."

Abbas, the outgoing Palestinian premier, refused to do this by force, appealing to the militants to voluntarily lay down their arms. Abbas resigned on Saturday, frustrated with four months in office in which he repeatedly wrangled with Arafat and failed to persuade Israel to ease security measures imposed on Palestinians.

Ahmed Qureia, whom Arafat has asked to become the new Palestinian prime minister, expressed "our regrets and pain for the innocent lives (lost) as a result of violence and counter-violence" and called on Israeli leaders to "search for ways to end this killing."

Qureia -- a former top peace negotiator -- has sought guarantees that if he accepts the post, Israel would do more to implement its obligations under the "road map." Israel has not frozen settlement-building or withdrawn from most Palestinian towns, saying the Palestinians must first dismantle militant groups as called for by the plan.

A senior Israeli official said on condition of anonymity that Qureia's terms were not acceptable.

"We will judge any Palestinian prime minister by his actions," Foreign Minister Silvan Shalom said in a statement. "He will have to decide whether he stands with Arafat or whether he stands against terrorism."

Qureia said he will "not be under an Israeli dictate" but reiterated that the Palestinians are "committed to the road map" -- a blueprint for ending violence and establishing a Palestinian state by 2005.

He and other Palestinian leaders accuse the Israelis of making the situation worse by carrying out a series of airstrikes against Hamas militants following last month's homicide bombing aboard a Jerusalem bus. Those strikes have killed 12 Hamas members and five bystanders.