Jerusalem ? The Israeli military’s legal adviser reportedly proposed tightening criteria for targeted killings of Palestinian extremists just as five members of a radical Palestinian group were slain Monday in what Palestinians said was the latest Israeli assassination of suspected militants.

Israel remained silent about its role in Monday’s deaths, but the attack focused new attention on the controversial Israeli policy in which dozens of Palestinians accused of terrorism have been killed.

Palestinian security officials said Israeli helicopters fired missiles at a car carrying five members of the Democratic Front for the Liberation of Palestine near Rafah in the Gaza Strip. The attack left the car a mass of twisted, smoldering metal and killed four passengers instantly; a fifth died later.

Israel had no comment on the strike, but the DFLP, a radical wing of Palestinian leader Yasser Arafat’s PLO, threatened revenge in a leaflet that promised to “very soon … shake the land under the feet of the occupiers.”

The Israeli daily Haaretz reported Monday that the military’s legal adviser prepared an opinion advising a tightening of the criteria for “targeted killings.”

According to Haaretz, the judge advocate general said such killings could be carried out only if there was clear evidence the target was about to plan or carry out a terror attack and could not be arrested. The guidelines ban killings as retribution for past attacks, it said.

Since Israeli-Palestinian violence broke out 16 months ago, dozens of militants and many bystanders have died in “targeted killings,” which Israel says are self-defense against those who plan attacks on its civilians.

Palestinians bitterly denounce what they term a policy of political assassinations such as August’s killing of Mustafa Zibri, who headed the Popular Front for the Liberation of Palestine. The United States has criticized the policy and human rights groups say it violates international law.

Israeli Foreign Minister Shimon Peres defended the practice Monday, saying the people Israel targets are “ticking bombs.”

“When you have a suicide bomber, if you don’t stop him ahead of time, he will kill people,” Peres said in New York, where attended the World Economic Forum.

In Israel, critics charge the killings are ineffectual and simply provoke more violence. “No assassination ended the suicide attacks” against Israel, commentator Michal Aharoni wrote in the Maariv newspaper.

A case in point was the Jan. 14 death of Raed Karmi, who headed the Al Aqsa Brigades a militia affiliated with Arafat’s Fatah in the West Bank town of Tulkarem. Karmi, who had boasted of killing two Tel Aviv restaurateurs last year, died in an explosion widely attributed to Israel.

His death had been preceded by more than a month without Israeli civilian deaths the longest such period since fighting erupted in September 2000 and it swiftly put an end to the lull; 11 Israelis and an American died in revenge attacks.

Israeli officials refused to confirm or deny the Haaretz report.

But a senior Israeli defense official, who spoke on condition of anonymity, said Israel never carried out revenge killings but rather targeted those who would have killed men, women and children.