The announcement came after the assassination of Ibrahim Hashash during an operation in the northern West Bank on Thursday.

In the Balata refugee camp on the outskirts of Nablus, a stronghold of the brigades, a local leader of the organisation vowed that his group would respond to the shooting.

"This assassination is a clear violation of the Israeli ceasefire," Ala Sanakri said.

Israeli sources said Hashash had been planning a shooting attack in Jerusalem and responded to an attempt to arrest him by opening fire at the soldiers.

The soldiers returned fire, wounding the 23-year-old who died shortly afterwards despite receiving treatment at an army post, the sources said.

Killing condemned

Palestinian President Mahmud Abbas accused Israel of violating the ceasefire agreement after Hashash's killing.

Abbas said the shooting was "a totally unjustified violation of the arrangements from Sharm al-Shaikh", while his national security adviser Jibril al-Rajub accused "certain circles within Israel of looking for pretexts to carry out such actions to sabotage the truce".

Groups such as al-Aqsa have
been observing a quiet period

Israeli Prime Minister Ariel Sharon and Abbas announced an end to more than four years of hostilities at a summit in the Egyptian resort of Sharm al-Shaikh on 8 February.

Israel pledged to end search operations for wanted Palestinian fighters, except those regarded as imminent threats.

Palestinian armed groups such as al-Aqsa, which had been observing an unofficial quiet period since late January, agreed last month at talks in Cairo to extend the period until the end of the year.

Elsewhere in the West Bank, a Palestinian was lightly wounded on Thursday by gunfire after Jewish settlers shot at his car near Hebron, Palestinian witnesses said.