Israeli forces killed at least eight Palestinians in an air strike and a ground operation Wednesday, the bloodiest day in the Gaza Strip since Israel declared it a "hostile territory," and four of the dead were identified as members of a militant group involved in kidnapping a BBC journalist and capturing an Israeli soldier.

Twenty-five Palestinians were wounded, Palestinian hospital officials said.

Israel said it was responding to ongoing rocket and mortar fire from Gaza at Israeli border towns, including 20 mortar rounds and 10 rockets on Wednesday. In the air strike, Israeli aircraft fired missiles at a jeep the army said carried rockets ready to fire. In the ground incursion, tanks took control of the northern Gaza town of Beit Hanoun, from where militants had launched rockets.

Israeli Defense Minister Ehud Barak warned Wednesday that "we are moving closer to a broad and complex operation in Gaza" to stop rocket fire, though security officials said a large-scale offensive is likely still weeks away. Last week, Israel declared Hamas-ruled Gaza a "hostile territory," as a precursor to a possible cutoff of electricity and other utilities.

In the West Bank, meanwhile, Palestinian security officials seized two homemade rockets, a possible sign that the techniques of Gaza militants were spreading. The crude projectiles, not yet fitted with explosives, were discovered in the West Bank town of Bethlehem and were handed to the Israeli army for inspection.

In Wednesday's airstrike, missiles hit a jeep as it crossed a crowded intersection in the Zeitoun neighborhood of Gaza City.

The bodies taken from the jeep were badly disfigured, prompting different death tolls. Hospital officials said four people in the jeep were killed, while the Army of Islam said five of its members were killed.

Dozens of Palestinians surrounded the wreckage, some dipping their hands into the blood of the victims, to underscore their demand for revenge. "God is great," the crowd chanted. Several cars were hit by shrapnel, and the force of the explosion shattered nearby windows.

The Army of Islam, a tiny militant group, started as a Hamas breakaway group, but whose current ties to Hamas are murky. Hamas identified one of those killed as Ayman Daloul, a field commander in the Army of Islam.

The Army of Islam was involved in the March kidnapping of BBC journalist Alan Johnston, who has since been released. The group is also believed to be among those holding Israeli soldier Gilad Shalit, seized in a cross-border raid in June 2006.

In the Beit Hanoun operation, witnesses said an Israeli tank shell fell between two houses and that soldiers also fired from tank-mounted machine guns. In all, four Palestinians were killed and 25 wounded by army fire, including five critically, hospital doctors said

Army bulldozers also piled up earthen mounds, apparently to restrict the movement of vehicles.

David Baker, an Israeli government spokesman, said the air strike is part of a "continuous policy of preventing terrorist activity against our civilians, including our taking pre-emptive measures as needed to thwart these attacks."

Atop aide to the head of the Hamas government in Gaza, Ismail Haniyeh, said the Israeli operations strengthened the resolve of Gazans. "The honorable Palestinian blood shed by this Nazi army will only make us more steadfast," said the aide, Mohammed Madhoun.

In other developments:

— The Israeli military announced an open-ended closure on the West Bank and Gaza Strip Wednesday, ahead of the weeklong Jewish holiday of Succot, which began at sunset Wednesday. Blanket closures, including travel bans within the Palestinian areas, are imposed during Jewish holidays, and restrictions are eased — though not lifted — once the holidays are over.

— The U.N. humanitarian coordinator, Kevin Kennedy, condemned the shelling of Gaza's crossings by Palestinian militants, saying such attacks only worsen what he described as a serious humanitarian situation in Gaza. Kennedy said that in the past week, only 97 trucks were able to enter Gaza, down 50 percent in a similar period in July, and warned of a shortage of dairy and perishable foods if the crossings are not opened soon .Israel has severely restricted the flow of cargo and people through Gaza's crossings since Hamas took control of the coastal strip in June.