Israeli troops shot dead a Palestinian gunman early on Thursday in the West Bank town of Nablus. The killing was the latest in a surge of violence that has shattered a three-week lull in more than 15 months of bloodshed since the Palestinians began an uprising against Israeli occupation in September 2000.

Israel responded to the new spasm of violence with a blockade around the West Bank towns of Tulkarm and Nablus on Tuesday after an upsurge in violence which followed the death of the Tulkarm leader of the al-Aqsa Martyrs Brigade, Raed al-Karmi, on Monday.

On Wednesday, the al-Aqsa Martyrs Brigade called on all radical Palestinian movements to attack Israel, after earlier abandoning a self-declared ceasefire.

Israel tightened the closure around three other Palestinian towns in the northern West Bank on Thursday amid the warnings that Palestinian militants were planning attacks.

Troops surrounded Qalqilyah and Jenin on Wednesday night, stopping Palestinians from leaving or entering the towns.

Dispute over PFLP leader arrest

Representatives of all the PLO factions, Hamas and Islamic Jihad met in Damascus last night to demand the "immediate release" of Ahmed Saadat, leader of the Popular Front for Liberation of Palestine, PFLP, who was arrested by the Palestinian Authority in Ramallah on Tuesday.

Israel accuses Saadat of being responsible for murdering Israeli tourism minister Rehavam Zeevi in October.

Israel’s prime minister, Ariel Sharon, has refused to lift a ban on Yasser Arafat which confines the Palestinian leader to his base in Ramallah until Saadat and three other PFLP men it accuses for the killing are arrested.

Despite pressure from the US, Russia, the EU and the UN, Mr Arafat refused to arrest Saadat. He is thought to have changed his mind due to preparations made by the Israeli army for another round of attacks on the Palestinian Authority.

Sharon has reacted with scepticism to the news of the arrest. Israel says it wants proof that Palestinian police have arrested Mr Saadat. "Until I see him behind bars, I won't believe it," Raanan Gissin, an adviser to Israeli Prime Minister Ariel Sharon, told Reuters news agency.

The Popular Front for the Liberation of Palestine (PFLP) has warned that a conflict may arise over the arrest of its leader, Ahmad Saadat, by the Palestinian Authority.

"The authority should know that what it did will put it in full confrontation with all the national and Islamist factions without exception," PFLP spokesman Maher al-Tahir said .

Hundreds of Palestinians took to the streets of Bethlehem on Wednesday to protest against Saadat's arrest, demanding his release.

On Thursday Sharon met with the foreign minister of Spain, Josep Pique, whose country holds the rotating EU presidency. Spain has offered to mediate in the conflict.

And Israeli and US officials have said that Israeli army chief Shaul Mofaz was on his way to the US to meet US Middle East troubleshooter Anthony Zinni. However, UN Middle East envoy Terje-Roed Larsen said hopes of a breakthrough were receding. "I'm afraid that opportunity is now slipping away from us. I'm deeply worried the resurging violence over the past few days, the killings...are all steps in the dance of death," Larsen told Reuters.

At least 805 Palestinians and 240 Israelis have been killed since the Palestinian uprising against Israeli occupation in September 2000.