Six people died in a series of violent incidents on Tuesday in the West Bank and Gaza Strip, shaking an already fragile four-month-old cease-fire between Israel and the Palestinians.

Israeli soldiers killed a senior leader of the radical Islamic Jihad movement whom they had gone to arrest in the West Bank town of Kabatiya, as well as a Palestinian gunman who fired on them during the operation, according to army officials. Later in the day, a Palestinian mortar attack on a Jewish settlement in the Gaza Strip killed three workers -- two Palestinians and a Chinese national -- and wounded four others.

The sixth person killed was an unarmed man who was shot by Israeli soldiers as he tried to scale the fence separating Egypt from Gaza, according to the army. His identity was unknown.

Israeli and Palestinian officials blamed each other for the renewed violence and said the attacks jeopardized the informal cease-fire hammered out among rival Palestinian groups and agreed to Feb. 8 by the Palestinian leader Mahmoud Abbas and Israeli Prime Minister Ariel Sharon. But each side also insisted it was not pulling out of the agreement, which was an attempt to end more than four years of violence and served as a prelude to the Israeli government's planned withdrawal of its soldiers and settlers from Gaza and parts of the West Bank, scheduled to begin Aug. 15.

The clashes added to tensions building since Monday morning when stone-throwing Palestinians clashed with Israeli police at the disputed holy site in Jerusalem revered by Muslims as the Noble Sanctuary and by Jews as Temple Mount.

Each side is also struggling with internal disputes. Leaders of Hamas, the militant Islamic movement, have protested Abbas's decision last weekend to postpone parliamentary elections scheduled for mid-July. At the same time, Israelis protesting the planned pullout from Gaza applied super-glue to the door locks at government offices over the weekend and poured sand into the gas tanks of some of the heavy vehicles designated for use in the evacuation.

The violence on Tuesday began when Israeli forces surrounded the house of Morwah Kamil, 25, head of Islamic Jihad's military wing in the northern West Bank city of Jenin. Kamil and a second man were killed during an ensuing gun battle.

The Israelis had information that Kamil was organizing a major terrorist attack on an Israeli city, according to an army spokeswoman, Yael Hartman. She said soldiers opened fire after Kamil threw a grenade at them. Witnesses said dozens of Palestinians gathered during the shootout and threw rocks and bottles at the soldiers. Palestinians said the second man killed was an unarmed policeman.

Islamic Jihad issued a statement saying that the Israelis had targeted Kamil for assassination in violation of the cease-fire and that the group pledged to avenge his death. "No one can request us to be patient anymore," the statement said. "This issue will not pass without a response."

Israeli officials said the action did not violate the cease-fire because Kamil was involved in ongoing armed activity.

Later in the day, Palestinians fired a mortar shell into a greenhouse in Ganei Tal, one of the Gaza settlements that is due to be evacuated in August. Islamic Jihad asserted responsibility for the attack, which killed the three workers.

Palestinians in Gaza also fired at least seven homemade rockets at the southern Israeli town of Sderot and other areas in the western Negev desert on Tuesday, hitting one house but causing no injuries. Hamas, formally known as the Islamic Resistance Movement, said its forces fired the rockets in retaliation for the attempt by Jewish visitors to tour the holy site in Jerusalem on Monday.

The cease-fire has been bent but not broken in recent weeks by similar incidents, and Israeli officials insisted they would continue to honor it. But they warned that Islamic Jihad appeared determined to rupture the truce.

Israel's new army chief of staff, Lt. Gen. Dan Halutz, told reporters that Abbas's Palestinian Authority needed to ensure the cease-fire was enforced among all Palestinian groups. If not, he warned, "it will first and foremost harm the Palestinians themselves."

Special correspondent Samuel Sockol contributed to this report.

An Israeli security officer treats a Palestinian worker wounded in a Palestinian mortar attack at a Gaza settlement.