JERUSALEM — Islamic Jihad militants in Gaza fired more than a dozen rockets at southern Israel early Thursday after Israeli undercover forces killed one of its West Bank leaders, shattering a recent lull in Gaza fighting.

The new violence highlighted the fragility of efforts to move Israel and Gaza's Islamic Hamas rulers toward an informal truce.

The Islamic Jihad commander Mohammed Shehadeh was buried Thursday in the West Bank town of Bethlehem along with three other gunmen killed in the raid late Wednesday. The bodies of Shehadeh and another militant were wrapped in Hezbollah flags, and dozens of mourners chanted support for the Lebanese guerrilla group — a sign of the Iranian-backed militia's growing influence on Palestinian militants.

A dozen rockets and three mortars were fired at Israel late Wednesday and early Thursday, Israeli security officials said. Two rockets struck a warehouse and soccer stadium in the rocket-weary Israeli town of Sderot, but no one was injured. Israeli aircraft struck a loaded rocket launcher early Thursday, but no Palestinian injuries were reported.

The rocket barrage from Gaza seemed inevitable after Israeli undercover forces opened fire on the car carrying Shehadeh. The Israeli military said the Islamic Jihad commander planned suicide bombings that killed dozens of Israelis.

Israeli Defense Minister Ehud Barak said Israel would keep pursuing militants involved in attacks in Israelis.

"Yesterday in Bethlehem we demonstrated once again that the state of Israel will continue to pursue and strike all murderers with Jewish blood on their hands," Barak said.

Israel held Hamas responsible for the rocket attacks because it controls the Gaza Strip.

"When another group takes responsibility for a rocket launch, they are subcontracting out for Hamas," government spokesman Mark Regev said. "No one could be firing rockets from Gaza without the support of Hamas."

Regev had no comment on an Army Radio report that Egyptian intelligence chief Omar Suleiman was due in Israel next week to try to advance truce efforts. Israel has publicly denied that any informal cease-fire was taking shape, though officials have privately acknowledged that Egyptian-brokered attempts were under way.

In Gaza, about 3,000 Palestinians marched to protest the Israeli raid in Bethlehem, and Hamas blamed Israel for the spike in violence. Spokesman Abu Obeid threatened retaliation against "all of the Zionist colonies and towns around Gaza."

A statement from the office of moderate Palestinian President Mahmoud Abbas, Israel's partner in troubled peace negotiations, condemned Israel's "ugly crime" in Bethlehem.

"The Palestinian Authority holds the government of Israel responsible for all the consequences resulting from these brutal crimes against our people," the statement said.

The latest spiral of violence began just hours after Hamas' prime minister in Gaza, Ismail Haniyeh, called for a period of calm with Israel. Before the Bethlehem raid, there had been signs Israel and Hamas were moving closer toward a cease-fire, including an ebb in fighting after clashes in previous weeks killed more than 120 people, nearly all of them Palestinians.

It was clear from Haniyeh's speech that his conditions for a truce include a halt to Israeli military operations in both the West Bank and Gaza.

"We are not going to divide Gaza and isolate Gaza from the rest of the land of Palestine," he said. "Gaza and the West Bank are part of the Palestinian homeland."

In another development, a Palestinian gunman who killed eight students at a Jerusalem seminary last week was buried late Wednesday, Israeli police spokesman Micky Rosenfeld said.

Police had held the body of Alaa Abu Dheim until his family agreed to hold a low-key funeral without media coverage, fearing a mass funeral could spiral into a riot by militant supporters. The burial took place without incident, in the presence of a small number of relatives, Rosenfeld said.

Abu Dheim, a 25-year-old resident of east Jerusalem, was shot dead at the scene of the attack by an off-duty army officer living nearby.

A previously unknown group with possible links to Lebanese Hezbollah guerrillas has claimed responsibility for the shooting. The claim has not been verified, but Israeli officials suspect Hezbollah or Hamas might have been behind the shooting.