A car packed with explosives pulled up to a bus in northern Israel during rush hour Monday, igniting a massive fireball that trapped passengers in the blazing bus and killed at least 16 people, including two homicide attackers.

About 45 people were wounded in the blast at Karkur Junction, several miles east of the town of Hadera. The army said 15 of the wounded were soldiers. The body of at least one soldier was seen lying next to the bus.

The explosion unleashed intense flames that sent huge plumes of smoke into the sky and initially prevented police and rescue workers from approaching the bus. When the fire was extinguished an hour later, the bus and the car were reduced to blackened skeletons.

"The explosion was so strong that I fell to the floor," Michael Itzhaki, a passenger who was sitting behind the bus driver, told Army Radio. "I looked back and quickly got off the bus, then it burst into flames."

"We succeeded in getting one soldier off the bus," Itzhaki said. "Two minutes after that, more explosions started ... and we couldn't get on the bus because it was on fire. Some of the soldiers climbed out the windows and survived."

The militant Islamic Jihad movement claimed responsibility in a letter faxed to The Associated Press, in Beirut, Lebanon. The group said the attack was in "retaliation for the series of massacres committed by the criminal enemy against our people." It cited recent Israeli military operations that have resulted in Palestinian civilian deaths in the West Bank and Gaza Strip.

The bombing raised the prospect of tough Israeli retaliation, and Public Security Minister Uzi Landau called for disbanding the Palestinian security forces. "We must not take our feet off the gas pedal, and keep acting with the utmost thoroughness in all the pockets of Palestinian terror," he said.

The army's chief spokeswoman, Brig. Gen. Ruth Yaron, did not say what the likely response would be, but linked the attacks to the recent easing of curfews in some West Bank towns.

"We'll have to be very careful now, there are probably more ticking bombs on the way," she said. "We have to re-evaluate the situation and see if we have any information on where the next attack might be coming from."

Military officials said on condition of anonymity that the curfews in West Bank towns and closures around them would be tightened and humanitarian aide would be restricted.

Israel has imposed curfews on hundreds of thousands in the West Bank's Palestinian cities for the past four months, a move that has brought a sharp decline in bombing attacks, but not their complete cessation.

Ron Ratner, a spokesman for the Egged bus company, said security officers in cars are trailing buses, watching for bombers.

"There was such a vehicle tens of meters from the car bomb," he said.

A rescue worker, speaking on condition of anonymity, said there was also an armed guard on the bus, but there was nothing he could do.

The bus began its trip in northern Israel and was headed south to Tel Aviv. It was stopped at a traffic light when the explosives-laden car pulled up beside it, police said. Israeli television, citing police, said more than 220 pounds of explosives were in the car.

The wounded included a 2-year-old girl who was seriously injured, according to rescue workers.

In Washington, White House spokesman Ari Fleischer said President Bush condemned the attack. "It's another reminder of how it's so important for peace to be pursued and for terror to be stopped," Fleischer told reporters.

Mark Sofer, a spokesman for Israel's Foreign Ministry, said the attack was intended to undermine the visit of Assistant Secretary of State William Burns, who is to arrive in Israel on Wednesday.

"Palestinian groups seized the opportunity to carry out yet another murderous attack inside of Israel aimed at innocent civilians, and one can only wonder and wonder again what do they want to achieve except for death, death and more death of innocent people."

Arafat, speaking in Ramallah, said: "You know that the Palestinian leadership position is against such attacks that target civilians, Israelis or Palestinians."

Israel has said it holds Arafat ultimately responsible, arguing his security forces have not made a serious attempt to prevent attacks. The Palestinians say Israel's devastating military strikes have rendered their security forces impotent against the militants.

Israel responded to a major bomb attack in September with a 10-day siege of Arafat in which its tanks destroyed much of what was left of his Ramallah compound. Palestinian bombings always revive talk among hard-line Israeli Cabinet ministers of expelling the Palestinian leader from the region.

The car apparently came from the Jenin area, in the northern West Bank, police commander Yaakov Borofsky told Israeli Radio.

Palestinian militants have carried out dozens of bomb attacks in the past two years of Mideast violence, and the Hadera area has been a frequent target. The town, though near the Mediterranean coast, is about 10 miles from the West Bank, where many homicide bombers come from.

Buses traveling to or from Hadera in northern Israel have been attacked numerous times. And a homicide bomber from Islamic Jihad pulled his car next to a bus on June 5 and detonated his explosives, killing 16 passengers near Meggido, about 15 miles northeast of Hadera.