Five members of a radical Palestinian group were killed Monday in an explosion in the Gaza Strip.
Palestinians say the men were killed when their car was blown apart in an Israeli missile attack near the town of Rafah, in the southern Gaza Strip.
The bodies were badly charred, and the car was destroyed in the explosion.
Witnesses say Israeli aircraft were flying over the area at the time of the blast.
An army spokeswoman says the Israeli military "has no knowledge of such an event."
The men who were killed were identified as members of the Democratic Front for the Liberation of Palestine (DFLP).
The DFLP is among the Palestinian militant groups that have carried out attacks on Israelis during more than 16 months of violence.
A spokesman for the group threatened revenge for the latest deaths.
Palestinian leader Yasser Arafat told reporters "what happened in Gaza shows that the Israeli government doesn't want calm, but wants an escalation against the Palestinian people."
Palestinian Information Minister Yasser Abed Rabbo said Israeli Prime Minister Ariel Sharon turned down a request to suspend targeted killings for ten days, to allow Palestinian security forces to restore calm.
Mr. Abed Rabbo accused the Israeli prime minister of destroying the peace process by using assassinations "as a permanent strategy."
Last month's killing of a Palestinian militia leader in an explosion blamed on Israel triggered a series of deadly revenge attacks in Jerusalem and Tel Aviv.
The daily Haaretz newspaper reported that the Israeli military's legal adviser has drawn up conditions to be met before the government can authorize the killing of a suspected militant.
It quotes the military's judge advocate general as saying there must be clear information that the target is planning to carrying out a terror attack in the near future.
The official reportedly ruled out punitive assassinations carried out in retaliation for previous attacks.
The car explosion took place hours after Israeli combat helicopters fired missiles at what the army says was a Palestinian mortar factory in the Jabalya refugee camp near Gaza City.
The missiles destroyed the building, but there were no reports of injuries.
The army says the assault was in response to mortar attacks in recent days on Israeli targets in Gaza.