Israeli helicopters on Thursday fired missiles at a jeep carrying four Palestinian gunmen and killed two, but Israel's declared target, a local militia chief blamed for the deaths of six Israelis, escaped with light injuries.

The missile attack in the West Bank town of Tulkarem came as Israeli Foreign Minister Shimon Peres and Palestinian leader Yasser Arafat were preparing an agenda for truce talks, possibly to be held next week.

Palestinian Planning Minister Nabil Shaath said the missile attack was undercutting cease-fire efforts. "It is a crime, a declared murder. This policy has to stop now," Shaath said.

The targeted man, Raed Karmi, was in a jeep driving near the Nur Shams refugee camp on the outskirts of Tulkarem when the first missile hit the ground behind the vehicle, said Karmi's bodyguard and driver, Hazem Kattab.

Karmi, 27, and Kattab jumped out of the vehicle, the witness said. A second and third missile hit the jeep directly, killing the two men in the back, identified as Omar Subuh and Mustafa Unbouth, both 20.

The two survivors were hurt by shrapnel and were taken to Tulkarem hospital, doctors said. Three bystanders were also injured.

"Unfortunately, we did not achieve our main goal," Gideon Meir, an Israeli Foreign Ministry official, said when it became apparent Karmi had not been killed.

Karmi is the local leader of the Al Aqsa Brigade, a band of Palestinian gunmen, most of whom are also members of Palestinian leader Yasser Arafat's Fatah faction.

The Israeli army said Karmi has been involved in numerous shooting attacks that have killed six Israelis and wounded several others. The army said Karmi received his orders and money from Marwan Barghouti, a senior Fatah leader in the West Bank and one of Arafat's lieutenants.

Meir said the missile strike came in response to recent attacks on Israelis.

"In the past few days, we have witnessed a series of bombs, targeting innocent women and children in Israel," Meir said, but did not elaborate on Karmi's possible involvement.

The army says Karmi was among gunmen who in January abducted two Israelis from a Tulkarem restaurant, took them to a remote area and killed them, execution-style. In response, Israel's then-prime minister, Ehud Barak, briefly suspended a last-ditch round of peace talks in Taba, Egypt.

One of the assailants later said he had targeted the two Israelis, owners of a sushi restaurant in Tel Aviv, to avenge the killing of his uncle Thabet Thabet, the Tulkarem Fatah leader gunned down by Israeli commandos outside his home in December.

Israel has killed about 50 Palestinians in its attacks targeting Palestinian militants it accuses of involvement in bombings and shootings of Israelis. Several of the victims have been bystanders, including two children.

Shaath, the Palestinian planning minister, accused Israeli Prime Minister Ariel Sharon of trying to sabotage a possible Peres-Arafat meeting.

In preparation for truce talks, the Palestinians have again raised the demand that foreign observers monitor a cease-fire. Israeli media reports have said Peres was open to the idea.

However, Sharon said he would not accept observers under any circumstances. "Israel's stand is well known. There will not be international observers," Sharon said Thursday, after returning from a four-day trip to Russia.

Later Thursday, Sharon was to convene his Cabinet for a special debate on a plan to set up a military "buffer zone" in the West Bank that would be off-limits to Palestinians and permit troops to arrest intruders.

The zone would run east of the so-called Green Line, the invisible frontier between Israel and the West Bank, and the objective would be to keep Palestinian militants out of Israel.

However, the Palestinians said Israel was imposing collective punishment. Israeli commentators said the plan would unilaterally alter the status of parts of the West Bank, as laid down in interim peace agreements.

The Israeli army was to have presented the plan at a news conference Wednesday, but Sharon stopped publication at the last minute and instead scheduled a Cabinet debate. He suggested he was delaying, not canceling the plan. "It's a process that is meant to happen in the future," he said.