Palestinian militants from Hamas called for a fresh wave of attacks against Israel after troops killed nine Palestinians in weekend fighting.
President Mahmoud Abbas' more moderate Fatah movement responded to the bloodshed by urging him to consider breaking off contacts with the Israeli government, despite his pledge to the United States to hold regular meetings with Israeli Prime Minister Ehud Olmert. Hamas and Fatah are serving in a joint Palestinian government.
Hamas, which has killed scores of Israelis in suicide bombings, sought to rally other Palestinian militant groups in a new offensive which would shatter the Gaza truce.
"The blood of our people is not cheap," a Hamas statement said, inviting Palestinians of every ideological stripe to unite and "use all possible means of resistance and to respond to the massacres."
Fatah also called for measures against Israel. "The Arab and the Palestinian leadership should evaluate the contacts with Olmert's government and reconsider these contacts and meetings," Fatah spokesman Abu Hakim Alwad said at a news conference in Gaza. "Israel is sabotaging the efforts made by the president to maintain calm and to strengthen the cease-fire."
Nine Palestinians were killed in the weekend upsurge of violence, including two gunmen and a 17-year-old killed Sunday in the West Bank. The fighting also included a Palestinian rocket attack on the southern Israeli town of Sderot that damaged a home.
Israeli officials defended the killings as part of operations that have drastically reduced the number of attacks against Israelis. Palestinian officials, however, said that the deaths jeopardized their efforts to expand the Gaza truce to the West Bank.
Miri Eisin, a spokeswoman for Olmert, said Israel "reaches out for peace, while at the same time we will always consistently fight against terror." Israel would continue its operations against Palestinian militants, she said, while "always doing our utmost to avoid any innocent casualties."
Troops killed the Palestinian teenager Sunday in a village near Ramallah. Palestinian officials said he was throwing stones at an Israeli patrol when he was shot. The army said soldiers opened fire as the youth was about to throw a firebomb at a military jeep.
Earlier, an army task force raided the militant stronghold of Nablus, killing two Palestinian gunmen, including Amin Lubadi, a top bombmaker who had been wanted by Israel for more than three years. The army said an Israeli soldier was lightly wounded in the gunbattle.
After weeks of relative quiet, the latest surge in violence began on Saturday, when five people were killed during Israeli arrest raids in the northern West Bank.
Palestinian officials said one of the dead was a 17-year-old girl shot by troops as she stood at the window of her home. The army said its soldiers had returned fire at a gunman in a window, but said the incident was being investigated.
In the Gaza Strip on Saturday, Palestinians fired a rocket at the Israeli town of Sderot, hitting a house but causing no injuries. The army subsequently attacked a car it said was carrying the attackers, killing a 37-year-old man. Palestinian officials said he was a civilian.
The Gaza truce has largely held, though militants have frequently fired rockets into Israel and have attacked Israeli patrols along the border fence. Israel has warned it will not tolerate continued rocket fire.
Israel is still in control of the West Bank, and unlike Gaza, that territory is dotted with Jewish settlements, making a cease-fire there a different issue. Israel has been reluctant to agree to a West Bank truce, concerned that militant groups would take advantage of it to hit settlers and prepare attacks in nearby Israel.
Israel sealed the West Bank and Gaza Strip early Sunday ahead of the country's Memorial Day for fallen soldiers, restricting the movement of Palestinians into Israel. Memorial Day begins at sundown on Sunday, followed by Independence Day, which begins Monday evening. The closure is expected to be in force at least until late Tuesday.