JERUSALEM -- Clashes and mortar fire in the West Bank and Gaza Strip killed six people Tuesday, one of the deadliest days of violence since Israel and the Palestinians declared a cease-fire four months ago.
While the two sides said they would still observe the truce, the fighting raised already heightened tensions and threatened nascent efforts to coordinate Israel's upcoming withdrawal from the Gaza Strip with the Palestinians.
"The situation is deteriorating. The whole cease-fire may collapse," said Palestinian negotiator Saeb Erekat, calling for international intervention.
The day's violence included a West Bank shootout in which two Islamic Jihad militants were killed, a mortar barrage that killed three non-Israeli laborers in a Jewish settlement in Gaza and the killing of a man who infiltrated Gaza from Egypt. Palestinian militants also fired an anti-tank missile and seven homemade rockets at Israeli targets, causing damage but no injuries.
Israel issued a stern warning for the Palestinians to rein in militants; the violent Palestinian groups Hamas and Islamic Jihad said Israel was responsible for the fighting.
Israeli Prime Minister Ariel Sharon and Abbas declared the cease-fire Feb. 8 in a bid to end more than four years of bloodshed. Since then, there has been a sharp drop in violence, though there have been occasional flare-ups.
On Tuesday, Israeli soldiers killed a top Islamic Jihad militant in the West Bank town of Jenin. Morwah Kamil, 25, head of the group's local military wing, was shot in a gunbattle that erupted after Israeli troops entered the nearby town of Qabatiya on an arrest raid.
A gunman who fired at soldiers was killed and five Palestinians were wounded, the army said.
Islamic Jihad pledged to retaliate. Hours later, Palestinian militants fired a mortar shell into a greenhouse in the Gaza Strip settlement of Ganei Tal. Two Palestinian and one Asian worker were killed and five other workers were wounded, one seriously, the army and hospital officials said.
Islamic Jihad claimed responsibility.
Later Tuesday, Palestinian police stopped another attempt to fire rockets at Israel from northern Gaza, said Interior Ministry spokesman Tawfiq Abu Khoussa.
He said a launcher and three rockets were confiscated, but the militants escaped. "We are doing our utmost to fulfill our obligations, enforce the law and make sure that declared truce is respected," he said.
The fighting clouded efforts to coordinate the Gaza withdrawal, which is to begin in August. Israel initially proposed the pullout as a unilateral move, but since the cease-fire, Israel has said it is willing to cooperate with the Palestinians.
"We have to tell the Palestinians a simple fact: There will be no coordination, meaning the disengagement will be unilateral, unless they crack down on their militants," said Cabinet minister Haim Ramon.
Ramon spoke shortly before Israeli and Palestinian officials met with James Wolfensohn, a special envoy on the Gaza withdrawal for the international community, and U.S. security envoy William Ward.