HAIFA, Israel ? A Palestinian suicide bomber killed at least eight Israelis in an attack on a crowded bus Wednesday, as Israeli forces hunting Palestinian militants moved deeper into two West Bank refugee camps.

The new escalation, on day 13 of Israel’s military offensive in the West Bank, created further difficulties for Secretary of State Colin Powell, who was to arrive in the region Thursday on a cease-fire mission.

Meanwhile, an Armenian monk was shot and wounded during the tense standoff at the Church of the Nativity in Bethlehem, marking the site where Jesus is said to have been born. Israeli troops have surrounded some 200 Palestinian gunmen holed up in the church along with some clergy for more than a week.

Palestinian policemen in the church and the Israeli army blamed each other for the shooting.

Israeli Prime Minister Ariel Sharon said it would be a “tragic mistake” for Powell to meet with Palestinian leader Yasser Arafat, who has been isolated in his Ramallah offices by Israeli troops for nearly two weeks. But Israel said it wouldn’t try to prevent such a meeting.

The Palestinians said they would demand of Powell that he secure Israel’s immediate withdrawal from four West Bank cities it still occupies. Israel’s security Cabinet ministers decided Wednesday that the offensive would continue, Israel Radio said.

Wednesday’s suicide bombing near the northern port city of Haifa was the second major attack on Israeli civilians since Israel launched “Operation Defensive Shield” on March 29 in an attempt to crush Palestinian militias. The bombing came a day after 15 Israeli soldiers were killed in West Bank fighting.

The Islamic militant group Hamas claimed responsibility for the Haifa blast, in which the bomber detonated explosives strapped to his body shortly after boarding a crowded bus at about 7:15 a.m. during rush hour.

Witnesses said the blast lifted the bus a few feet into the air. Much of the roof was peeled back, windows and tires were blown out, and the front of the bus was a twisted wreck. Rescuer workers arriving at the scene covered several bodies lying on the highway with sheets and blankets. Personal belongings were strewn across the asphalt, including an olive-colored jacket normally worn by soldiers, a skullcap and an identity card.

Eight passengers and the bomber were killed, and 14 people were wounded.

“It’s a catastrophe. Shrapnel and bits are everywhere,” one witness, identified only as Motti, told Israel Radio. “You have no idea what it is to see such a thing … people are thrown in all directions.”

Sharon adviser Raanan Gissin said the bombing was a sign that Israel could not be expected to keep withdrawing from Palestinian cities _ as the United States has demanded _ until it has hunted down Palestinian militants.

“If we don’t complete the job and dismantle the terrorist infrastructure and defeat terrorism, the chances to reach a cease-fire and move to a political process are dim,” he said. Israeli forces pulled out of two West Bank towns early Tuesday.

In Spain, Powell was joined by U.N. Secretary-General Kofi Annan and officials from the European Union and Russia in a joint call Wednesday for Israel to withdraw from Palestinian towns and a condemnation of suicide bombings. “Violence of whatever form … at this point is counterproductive,” Powell said. “It is totally destabilizing the region.”

Also Wednesday, Lebanese guerrillas fired more than a dozen rockets at the Israeli-annexed Golan Heights and northern Israel in one of the most extensive attacks since Israel withdrew from Lebanon nearly two years ago. One Israeli soldier was injured, and Israeli warplanes responded by firing missiles at suspected guerrilla positions in Lebanon.

Hezbollah guerrillas have fired frequently on Israeli positions in a disputed border area since the West Bank operation began, bringing Israeli accusations that they are trying to open a new front in the conflict.

In the West Bank refugee camp of Jenin, the scene of the deadliest fighting during Israel’s offensive, dozens of gunmen holed up in a small area fired sporadically Wednesday morning at Israeli troops advancing with bulldozers.

A Hamas leader in the area, Jamal Abdel Salam, said he received a phone call at midmorning from a member of Hamas’ military wing who said he and his comrades had run out of ammunition. “This is the last call,” Abdel Salam quoted the gunman as saying. “We are in a group inside a house. They (the Israelis) are at the door and they are coming to arrest us. Take care of my family.”

Later Wednesday, about 300 camp residents, including fighters, women and children, surrendered to Israeli troops. It was not clear if the fighting was over.

On Tuesday, 14 Israeli soldiers were killed in the camp _ 13 in an ambush and one in fighting later in the day.

The soldiers had stumbled into a sophisticated trap prepared by Palestinian gunmen. A group of soldiers entered the courtyard when dozens of linked charges went off, possibly detonated by a suicide bomber. The force and other soldiers rushing to their rescue then came under fire from gunmen on nearby rooftops.

The Israeli daily Maariv said the entire incident was photographed by a pilotless plane flying over the camp. “We saw flashes of the explosion and the people lying on the ground,” Maariv quoted one officer who saw the photos as saying.

More than 100 Palestinians are believed to have been killed in the Jenin camp, with many bodies still lying in the street. Among those reported dead was Mahmoud Tawalbeh, 23, a leader of the militant Islamic Jihad group who masterminded a number of suicide bombings in Israel.

In the West Bank city of Nablus, rescue workers on Wednesday retrieved the bodies of 14 Palestinians killed in the fighting, bringing the total confirmed dead in the city since the start of the Israeli invasion to 60. The old city of Nablus, a warren of narrow alleys, had been a flashpoint, with battles raging there for several days.

After noon, word spread through the old city that Israeli soldiers had left the area, and residents, who had been confined to their homes for more than a week by an Israeli curfew, came into the streets, inspecting the trail of destruction.

On the outskirts of Nablus, Israeli tanks and helicopters shelled the Al Ain refugee camp, damaging some homes. After daybreak, soldiers called over loudspeakers on teen-age boys and men to come out of their homes, and witnesses saw hundreds of Palestinian men sitting on the ground in front of the camp’s mosque.

The Israeli military said that since the start of the offensive, 28 Israeli soldiers have been killed, but has not provided a list of Palestinian casualties. The Palestinian Red Crescent said Tuesday that at least 128 Palestinians have been killed and 337 wounded, but that the toll was expected to rise significantly.

The army said it has detained more than 2,100 Palestinians, including 117 on Israel’s wanted list, and confiscated nearly 2,500 rifles.