NETANYA, Israel -- A suicide bomber burst into a hotel dining room and blew himself up Wednesday just as Israelis dressed in their holiday best were sitting down to a Seder meal celebrating the Jewish Passover. At least 19 Israelis were killed and more than 120 wounded.

The explosion tore through the ground floor of the Park Hotel in this northern coastal resort, blowing out walls and windows and overturning tables and chairs. Bits of rubble and wires dangled from the ceiling. In the chaos, one table remained standing, covered by a white cloth and with the elaborate Seder place settings still in place.

"Suddenly it was hell," said one of the guests, Nechama Donenhirsch, 52. "There was the smell of smoke and dust in my mouth and a ringing in my ears."

Hamas responsible

The Islamic militant group Hamas claimed responsibility for what Israeli government spokesman Gideon Meir called a "Passover massacre." The bomber, a 25-year-old Palestinian, had worked in Netanya hotels in the past.

The bombing in Netanya threatened to derail the latest U.S. truce mission, just hours after President Bush said his envoy to the region had made some progress. In later comments, Bush said "this callous, this cold-blooded killing, it must stop."

Israel, which had reluctantly accepted the latest U.S. cease-fire proposals, said it would have to reassess its policy and held Arafat responsible for the bombing. Police Minister Uzi Landau called for retaliation, saying the Palestinian Authority must be destroyed.

The Palestinian Authority said it "strongly condemned" the bombing, and that it would take tough measures against those involved. Palestinian security sources said Arafat ordered the arrests of four key militants in the West Bank.

Earlier reports said 16 Israelis were killed, but police officials said later that the figure had climbed to 19. The injury toll rose to more than 120, including more than two dozens who were in serious condition. It was one of the worst suicide bombings in the past 18 months of Israeli-Palestinian fighting. The deadliest was an attack in June outside a Tel Aviv disco that left 22 dead.

Passover Seder

The explosion occurred at about 7:20 p.m. Wednesday, as dozens of guests in the Park Hotel along Netanya's boardwalk settled down for the Passover Seder in the dining hall. Guests were dressed in their holiday best; the women in festive dresses, the men in white shirts and dark pants.

The bomber, carrying a large bag of explosives, made his way past an armed guard at the hotel entrance who did not consider him suspicious, Israel TV said. From the lobby, he ran toward the dining hall, where he blew himself up.

Donenhirsch, the guest, said that as she and her family fled, they saw a little girl, about 10 to 12 years old, lying dead on the ground, her eyes wide open as if in surprise.

Some of the wounded staggered out of the lobby, which was plunged into darkness by the explosion. Others were taken to ambulances in stretchers, including a young boy who had an oxygen mask pressed to the face.

One man was covered by a blue blanket, blood dripping from his face. An elderly woman, her face covered with blood, sat on the sidewalk, attended to by several people. Witnesses said they saw five bodies lined up on the pavement, some of them dismembered, including that of a woman in festive holiday clothes.

"They attacked innocent Israelis on one of the most sacred nights to Jewish people, Passover," said Meir, the Israeli government spokesman.

Israeli police had been on high alert for possible attacks during the weeklong Passover holiday, with more than 10,000 officers deployed in potential trouble spots.

The country's police commissioner, Shlomo Aharonishki, said it was impossible to prevent all attacks. "Even with more policemen and a broader deployment, we cannot block the centers of the cities," Aharonishki said.

Hamas identified the bomber as Abdel Baset Odeh, 25, from the West Bank town of Tulkarem. Palestinian security sources said Odeh was wanted by Israel and the Palestinians.

Israel has said repeatedly it cannot tolerate more attacks on its civilians. Earlier this week, Sharon convened his security Cabinet to discuss possible options in the event the truce mission fails. One idea raised was a large-scale military operation in the West Bank and Gaza Strip.

Israel has accused Arafat of doing nothing to rein in militants. Raanan Gissin, a Sharon adviser, said the attack in Netanya "will require us to reevaluate our overall policy."

"We are still working to achieve a cease-fire to which we are fully committed, but if the Palestinians have decided to choose the road of terrorism ... then we have to decide what measures we will take," Gissin said.

Secretary of State Colin Powell urged Arafat to go on television and demand an end to attacks against Israelis. The attacks endanger any negotiations toward a Palestinian state, Powell said.