A top member of the Islamic militant Hamas group, his deputy and his brother were killed during an Israeli helicopter strike in the West Bank town of Nablus Friday, Palestinian officials and Israel army radio said.

Mahmoud Abu Hanoud was head of Hamas' military wing and was high on Israel's most-wanted list, Hamas officials said. The group declared three days of mourning and called for a general strike throughout the West Bank and Gaza Strip on Saturday as a mark of protest.

Hamas officials initially denied that Abu Hanoud had been hit, but later acknowledged his death.

Also killed was the Hamas leader's deputy, Ayman Hashaykah, and Hashaykah's brother, a lower-ranking Hamas activist.

Their bodies were identified by Palestinian hospital officials, who said they had not yet identified any remains as those of Abu Hanoud.

The Israeli military refused to comment. Earlier reports from Israeli army radio and Palestinian officials said two Hamas members were killed in the attack but did not include Abu Hanoud among them.

The attack occurred on road between Nablus and the town of Jenin. Earlier, Israeli security forces had gone on alert after receiving intelligence that three armed Palestinians were on their way to carry out an attack inside Israel, they said. It was not known if the alert and the attack on the Hamas trio were connected.

A senior Hamas official has vowed that Israel will suffer a "painful response" for Abu Hanoud's death, Reuters said.

The three Hamas members were among seven Palestinians killed Friday, making it the deadliest day since Oct. 26, when 10 died in clashes with the Israeli military.

Israeli troops shot and killed a 15-year-old Palestinian while dispersing stone throwers in the Gaza Strip refugee camp of Khan Younis, where a day earlier five boys had been killed by what Palestinian police said was a bomb planted by Israeli forces. There were growing demands in Israel that the military make swift disclosure of its investigation into the deaths.

Also in Gaza, a Palestinian taxi driver was killed and three of his seven passengers were wounded when the vehicle came under Israel fire. Two of the wounded were critically hurt with head injuries, doctors said.

The army said troops opened fire at the car fearing it contained attackers after the driver approached an army post after dark and ignored orders to halt.

They said that the car had previously twice driven toward the post, then turned back before approaching for a third time.

Near the West Bank town of Nablus, two Palestinians were killed when a bomb they were trying to plant near a road used by Israeli motorists blew up prematurely, Palestinian security officials said.

Palestinian Cabinet Secretary Ahmed Abdel Rahman said the killing of the Hamas activists just a day after the deaths of the Gaza schoolchildren, suggested a deliberate attempt by Israeli Prime Minister Ariel Sharon to sabotage a new American push to calm the Israeli-Palestinian conflict.

"I think he wants to make the American effort fail and it is an attempt to push the Palestinians to react," he said.

In recent months, Israel has killed some 50 militants it suspected of involvement in bombing and shooting attacks on Israelis. More than a dozen bystanders have also died in such targeted killings. The United States has condemned the practice.

Friday's rocket attack killed Ayman Hashaykah, the No. 2 in the military wing of Hamas in the West Bank, Palestinian officials said. Hashaykah's brother, himself a Hamas activist, also died when the rockets hit the van as the pair traveled between Nablus and the town of Jenin, the officials said.

Hamas officials said the most wanted Palestinian in the West Bank, Mahmoud Abu Hanoud, head of the group's military wing, was not in the van.

Prior to the incident, Israeli security forces went on alert after receiving an intelligence warning that armed Palestinians were on their way to carry out an attack inside Israel, Israeli security sources said. It was not known if the alert and the attack on the Hashaykah brothers were connected.

In the Gaza Strip, thousands joined the funeral procession for the five boys killed in Thursday's blast. The victims ranged in age from seven to 14 and all members of the same clan.

After the funeral, about 200 Palestinians marched toward the nearby Jewish settlement of Neve Dekalim, throwing stones at the fence. Israeli troops fired stun grenades and live rounds, killing a 15-year-old boy, doctors said. The army said it fired warning shots in the air, and did not see anyone being hit.

Palestinians fired a mortar shell at Neve Dekalim, damaging a house but causing no casualties.

The Palestinian police chief in Gaza, Brig. Gen. Abdel Razek Majaida, said the boys appeared to have been killed by a bomb planted by Israeli forces, who had been seen operating in the area the night before the blast.

"Shrapnel we collected from the area shows that the explosion was caused by an explosive device," he said. "Our investigation continues, but it looks as if the device was booby-trapped and when one the children kicked it, it exploded."

Israel's defense minister said the blast was being investigated and expressed regret over the deaths. Israel officials refused to comment further pending the results of the inquiry, but two Israeli newspapers quoted army officers as saying that Israeli troops trying to thwart Palestinian sniper squads had recently operated in the area of the explosion.

Opposition leader Yossi Sarid called for the army to present the full facts of the case by the beginning of next week and for stern action to be taken if improper conduct is discovered.

"Somebody high up in the army will have to pay with his head," Sarid told Israeli television. "Children killed, whether on our side or theirs, is not something that can be passed over."

Palestinian Information Minister Yasser Abed Rabbo called on the United States and Europe to press Israel to pull its troops back from Palestinian population centers.

Two U.S. mediators, Assistant Secretary of State William Burns and retired Marine Corps Gen. Anthony Zinni, are to arrive in the region next week.

They are to press the two sides to implement accords already agreed on -- a truce negotiated last May by CIA director George Tenet, and the April report of an international commission headed by former U.S. Sen. George Mitchell with a formula for restarting peace talks.

Zinni, appointed special adviser to Secretary of State Colin Powell, is expected to remain in the area to shepherd the negotiations.

The Associated Press contributed to this report.