J By Laura King

ERUSALEM – At least one suspected Palestinian gunman infiltrated a remote Israeli kibbutz just across the border from the West Bank late Sunday, shooting at least five people dead, wounding three others and setting off a massive nighttime manhunt by Israeli troops using search dogs and helicopters, witnesses and officials said.

Flares lighted the sky as hundreds of police and soldiers scoured the low hills around Kibbutz Metzer in northern Israel, but the attacker (or attackers) escaped. Earlier in the day, the kibbutz had been the scene of an intercepted car bombing that killed two Palestinian men when their vehicle exploded.

Israeli retaliation was swift. Two hours after the attack on the collective farm, Israeli helicopters launched an airstrike on Gaza City before dawn Monday, firing rockets into the downtown area near the Mediterranean seaside. The Israeli army had no comment.

Kibbutz Metzer lies near the Green Line dividing Israel and the West Bank, not far from the Palestinian town of Tulkarm, which has often served as a staging ground for attacks during more than two years of intense Israeli-Palestinian violence.

Infiltrations by Palestinian militants of Jewish settlements in the West Bank and Gaza Strip have become commonplace during the fighting, but Sunday’s attack was one of the worst in memory against a kibbutz inside Israel proper.

The gunman, who authorities said was probably accompanied by an accomplice, slipped into the community shortly after midnight and fired at a family inside their home and at kibbutz residents who were leaving the communal dining hall after a late supper, authorities said.

Other residents, who had recently held a drill on how to cope with such an attack, huddled in their homes as the gunfire rang out. A woman who identified herself only as Irit told Israeli radio that the shooting went on for about 10 minutes before security forces arrived.

The district police chief, Yaakov Borovsky, told Israeli radio that based on the number and timing of the shots fired, it was believed there had been more than one assailant.

The Al Aqsa Martyrs Brigade, a militia linked to Palestinian leader Yasser Arafat’s Fatah faction, claimed responsibility for the shooting in telephone calls to Western news agencies. However, it is not unusual for more than one militant group to claim responsibility for the same attack.

Israeli officials said they suspected the shooting might have been the work of the same militants who had sent a fully primed car bomb across the border from the West Bank and into Israel earlier in the day. The vehicle blew up with a thunderous detonation when border police tried to stop it on a road close to the kibbutz.

It was not clear whether the powerful bomb was accidentally set off by the car’s two occupants or whether they deliberately triggered it when they realized they would not be able to reach their target. The blast reduced the car to a charred wreck.

The explosion was one of three foiled suicide bombings on Sunday, including one attempt by a 15-year-old boy who was captured in the West Bank city of Nablus as he set off on a bombing mission, Israeli officials said.

Another case involved a senior activist from the militant group Hamas, who was arrested overnight in the volatile West Bank city of Hebron. Israeli officials said he had masterminded an imminent bomb plot.

Also Sunday, despite multiple warnings of possible attacks, the army eased its grip on the West Bank city of Jenin, lifting a tight curfew for the first full day since Oct. 25. Families flocked to markets to shop for provisions for Ramadan meals, and bulldozers began clearing away debris.

Monday’s predawn rocket attack in Gaza City touched off a raging fire, eyewitnesses said. They said the target appeared to be a building they described as an auto-parts shop, believed to be empty at the time. Israel says what appear to be Palestinian industrial workshops are sometimes bomb factories.

The kibbutz attack was the most serious strike at Israelis since a shake-up last week in the Cabinet of Prime Minister Ariel Sharon, following the collapse of his parliamentary alliance with the left-leaning Labor Party.