The explosion ripped the roof off bus number 37, turned the vehicle into a charred wreck and hurled bodies out onto a main street in Israel's third largest city.

In apparent response, Israeli helicopters fired several missiles into a Palestinian refugee camp in the Gaza Strip early on Thursday and at least one person was killed, witnesses said.

They said Israeli tanks had entered the desert strip from Israel and encircled the densely-populated Jabalya camp, used by Islamic militants waging a 29-month-old uprising against Israel.

Israeli Prime Minister Ariel Sharon's inner security cabinet had met on Wednesday evening to consider how to respond to the Haifa bombing.

His rightist coalition, which took office a week ago after elections, has members seeking a harder line against the uprising for Palestinian statehood than the previous government and supporting calls for the expulsion of Palestinian President Yasser Arafat.

The bombing followed a series of army raids in the Gaza Strip and the West Bank in which 80 Palestinians, both gunmen and civilians, have been killed in the past five weeks -- a period in which eight Israelis were also killed.

"Body parts, hands, legs, glass and debris flew from the bus to right in front of the hairdresser salon," said Michael Afuta, 20, who works at the nearby hairdresser's.

"The salon shook from the force. Glass broke, lights went out. I ran to the bus but I was so scared of another blast that after a few seconds I came back... It was horrific."

Students at a local university were emerging from classes at the time of the blast.

No claim of responsibility was made for the bombing -- an unusual silence from Palestinian militant groups that have been behind scores of suicide attacks in Israel.

West Bank Link to Bombing

But Israeli military sources said the identity card of a Palestinian from the West Bank city of Hebron was found in the bus wreckage. Troops went to the man's family home there on Wednesday evening and detained his father and two brothers.

Palestinian witnesses identified the bomber as a 21-year-old activist for the Islamic militant group Hamas and said he had been missing for several days.

Police said the assailant had a large bomb strapped to his body. The blast from the nail-packed bomb, the trademark of suicide militants, sprayed nearby cars with blood and showered bus seats and victims' shoes onto the street.

Rescue workers draped several bodies still lying in the bus with blankets and one body was left hanging out of a window.

Police said at least 15 people were killed. It was not clear whether the figure included the bomber.

Israeli has recently stepped up raids into Gaza and the West Bank, stoking Palestinian fears of a tougher Israeli crackdown as the world focuses on possible war in Iraq.

The United States, which wants calm in the region before any war and rebuked Israel this week over its latest raid, led international condemnation of the blast. President Bush vowed to keep pursuing peace initiatives. Britain, France, Germany and Russia called for a fresh diplomatic process.

Arafat's Palestinian Authority condemned the attack.

The last suicide bombing in the Palestinian uprising was on January 5, when 23 people were killed in a Tel Aviv bus station and nearby pedestrian mall.

Intensified Israeli military blockades, curfews and raids in the West Bank since mid-2002 have slashed the number of suicide attacks but Israeli police say they continue to thwart bombing attempts almost daily.

"The Palestinian Authority has been doing absolutely nothing to stop this horrendous blood trail of killing and carnage. There was a deceptive lull in attacks mainly because of the success of our security services," said a government spokesman.

Arafat has said repeatedly that Palestinian security services cannot staunch the violence because they have been crippled by Israeli blockades, waves of arrests and demolition of infrastructure in the West Bank and Gaza Strip.

"The leadership announces its condemnation to this operation in which civilians, who are not part of the war of annihilation waged by the Israeli government against the Palestinian people, were killed," a Palestinian Authority statement said.

International peace moves are now focused on a nascent "road map" envisaging a Palestinian state sought by Arafat but unpalatable to many right-wingers in Sharon's government.

The toll before Wednesday's bloodshed was at least 1,891 Palestinians and 706 Israelis killed since the Palestinian revolt began in September 2000 after talks on a Palestinian state stalled.

(China Daily March 6, 2003)