The armed wings of two Palestinian guerrilla groups have vowed to intensify attacks throughout Israel, after two of their leaders were killed in an explosion the militants blame on the Israeli army. Israel has not accepted responsibility for the killings.

Israel is bracing itself for a new wave of terrorist attacks from Hamas and from the armed wing of Palestinian leader Yasser Arafat's Fatah faction.

Both groups are vowing revenge for the killing of two of their leaders, Imad Nastri, head of the Hamas military wing in the Jenin area, and Ala Al-Sabbagh, the local leader of Fatah's Al-Aqsa Martyrs Brigade.

Palestinian residents gave conflicting reports of their deaths. Some said the attack was carried out by an Israeli army helicopter. Others said a blast went off in their hideout in the Palestinian refugee camp in Jenin.

Both were on Israel's wanted list of suspected Palestinian terrorists, but Israeli military officials say no helicopters were operating in the Jenin area Tuesday night, when the explosion occurred.

The fact that the leaders of two different armed groups were meeting appears to highlight the growing co-operation between Palestinian militant groups in recent months.

In the past 12 months, Fatah has sometimes announced joint responsibility with Hamas for terrorist attacks, including suicide bombings.

Israel has responded to such attacks by mobilizing its troops across much of the West Bank.

Palestinians also say soldiers killed a Palestinian resident in a refugee camp near Nablus early Wednesday, as he was beating a drum to announce the start of the daily fast for the Muslim holy month of Ramadan.

Meanwhile, in the Gaza Strip a suspected would-be Palestinian suicide bomber was killed when the car he was driving, packed with explosives, blew up, close to a Jewish settlement.