JERUSALEM -- A Palestinian suicide bomber blew up a commuter bus packed with office workers and students during yesterday's morning rush hour, killing himself and 19 Israelis as President Bush prepared to outline his framework for Middle East peace in Washington.
Israel responded swiftly to the attack, saying it would retake parts of the West Bank and hold them as long as bombings continue, according to a government statement released early this morning.
The statement, issued after late-night consultations between Israeli Prime Minister Ariel Sharon and his top Cabinet ministers, said Israel's actions would include "a change in the way Israel responds to murderous acts of terror."
It said Israel would respond by "capturing Palestinian Authority territory. These areas will be held by Israel as long as terror continues."
Late last night, Israeli tanks rumbled into the West Bank city of Jenin, cutting the town off from an adjacent refugee camp and drawing fire from Palestinian gunmen. Apache helicopters were seen hovering, and warplanes made several passes over what Israel considers a militant stronghold.
Before daybreak, large numbers of Israeli tanks and troops entered Nablus, in the northern West Bank, from all directions, and attack helicopters flew overhead, witnesses said.
The Israelis arrested three suspects, then withdrew. Soldiers also arrested six Palestinians in the city of Hebron and two nearby villages.
The Israeli military refused to comment.
Cabinet aides said last night that a mass expulsion of Palestinian militants and possibly of officials close to Palestinian leader Yasser Arafat was also being considered. Still, Israel's Foreign Ministry urged restraint so as not to undermine Bush's initiative.
Yesterday's attack, the first in Jerusalem since April and the deadliest in the city in six years, occurred in the southern part of the city near the neighborhood of Gilo, built on the West Bank.
The explosion was powerful enough to lift the red and white bus off the ground and tear off its roof, leaving behind a pile of bodies, ripped clothes and book bags splattered with blood. More than 50 people were injured.
"I have been through wars and seen everything," said Shalom Sabog, 50, who was in a car behind the bus, watched it blow up and was among the first to help the injured. "It is beyond comprehension what I saw today."
Jews and Arabs were among the victims. The suicide bomber was described as a 22-year-old Palestinian graduate student from the West Bank al Faraa refugee camp who had made two previous attempts at bombings.
In an unusual move, Sharon toured the site of the blast, the first time he has visited the scene of a suicide bombing since taking office. Aides said top officials are urged to stay away from such places because of security concerns, and Sharon's visit was the first by a prime minister to a bombing in six years.
Sharon grimly walked around the remains of the charred bus and slowly shook his head as he passed by 11 black body bags lined up in a row on the sidewalk. His visit was intended to draw attention to Israel's suffering while sending a harsh message to Bush that there can be no Palestinian state with Arafat as its leader.
"What kind of a Palestinian state are we talking about?" Sharon asked. "The terrible pictures we see here are stronger than every word. ... This is the continuation of Palestinian terrorism. And this terrorism has to be fought and battled, and that is what we will do."
Bush has been expected to deliver a speech this week outlining a comprehensive plan to restore order in the Middle East, possibly including establishing a provisional Palestinian state and restarting negotiations between the warring sides.
The Islamic Resistance Movement, known as Hamas, claimed responsibility for the bombing and identified the attacker as Mohammed al-Ghoul, a student pursuing a master's degree in Islamic studies at Najah University in Nablus.
Hamas said he had infiltrated Israel from Bethlehem, a few miles from where the bus blew up. The group said last night that al-Ghoul had twice been thwarted trying to carry out a suicide attack, but it did not elaborate. Hamas opposes any negotiations with Israel.
"This time, I hope I will be able to do it," al-Ghoul said in his suicide note. "How beautiful it is to make my bomb shrapnel kill the enemy."
Palestinian officials condemned the blast, saying that attacks on civilians hurt their long-term interests of securing a homeland. One of Arafat's advisers, Ahmed Abdel-Rahman, urged Bush to declare a state immediately and send foreign troops to monitor both sides, saying it was the only way to ensure peace.
World leaders spoke out strongly against the attack, but they also pressed Sharon not to retaliate and scuttle the peace initiative.
Sharon has been building up pressure to push Arafat into obscurity, treat him as a figurehead and deal only with Palestinians whom he considers more moderate.
"What we have to do, before any negotiations, is to completely uproot terrorism," said Uzi Landau, Israel's right-wing public security minister, who accompanied Sharon to the bomb site. "Until then, there can be no speaking of a state or even a political horizon."
Last night, Sharon met with the heads of various intelligence agencies and the leaders of political factions in his coalition government, as well as with the security cabinet. Foreign Minister Shimon Peres cut short a visit to Eastern Europe to fly back to Israel.
Most army and intelligence officials continued to advise Sharon against expelling Arafat, arguing that he could be more dangerous abroad.
Past responses to attacks have included a broad six-week invasion of the West Bank and twice putting Arafat under siege with tanks, once for 34 days. Troops also have shot, shelled and bombed Arafat's compound in Ramallah, and virtually all the buildings there have been destroyed.
Yesterday's attack also bolstered calls for a fence separating the West Bank from Israel, and around Jerusalem. Construction started Sunday, but proponents pushed yesterday to speed up the pace. About 6 miles of a proposed 54-mile fence are in place around Jerusalem.
Yesterday's attacker apparently walked undetected into Jerusalem through a military checkpoint or skirted the army by walking through fields and olive groves.
Police in Jerusalem had been on high alert since Monday night, when they received intelligence that a bomber had gotten into the city and was looking for a place to blow up. Streets were shut down, and armed officers saturated the city.
The explosion ripped through southern Jerusalem about 8 a.m., but police said the bomber was not the person they had been looking for all night, and a manhunt for another attacker continued throughout the day.
"We think there is another suicide bomber right now on the streets of Jerusalem," said police spokesman Zrihen Koby. "We hope we can prevent it."
Witnesses said the bomber boarded at a stop outside Gilo without paying his fare and set off a nail-and-bolt-studded explosive hidden under a shirt or strapped to his waist seconds after the bus edged away from the curb.
People in the front of the bus, headed to the central station downtown, bore the brunt of the blast.
Its passengers represented a cross-section of Israel: young and old, Jewish and Israeli-Arab, lawyers on their way to work and students heading to school. Fourteen of the dead were from Gilo, including the youngest victim, an 11-year-old girl.
Many aboard were students from Ort Spanian high school, just 150 yards from the Patt Junction, where the explosion occurred. Other students were in morning prayers when someone rushed into the synagogue shouting about a bomb.
They rushed to the front gate and watched as emergency workers rushed to the bus in a frantic effort to save lives. It was unclear last night whether any of the students were among the dead, but school officials said at least seven students had been on the bus.
Cell phones jammed throughout the city as worried parents, relatives and friends tried to reach loved ones. Others ran to the scene in a panic. One woman tried to break through police lines, yelling, "My sister? Where is my sister?"
The man who was supposed to drive the bus yesterday was Amit Maliah. But he arrived to work a minute late. Rahamim Zidkiyahu, 51, scheduled to drive a later bus, volunteered so he could get home early to watch a World Cup soccer match.
Maliah took the next bus, six minutes later, and was one stop behind his co-worker when he heard the explosion. Zidkiyahu died with his hands still on the steering wheel. The father of three was buried last evening in Jerusalem.
Witnesses said most of the bodies were in the front of the bus, piled near the door.
Yesterday's bombing was the third-deadliest of the 19-month uprising. A blast March 27 at the Park Hotel in Netanya killed 29 people on the eve of Passover, and a June 1, 2001 attack at the Dolphinarium disco in Tel Aviv killed 21.
The Associated Press and The Chicago Tribune contributed to this article.