GAZA CITY, Gaza Strip ? An Israeli warplane attacked a house early today in a crowded, rundown Gaza City neighborhood, killing a leading Hamas militant and at least 11 other Palestinians, including several children.

The air strike came as Palestinians and Israelis were trading ideas to relieve tensions in the West Bank. It seemed likely to derail the efforts as Hamas threatened revenge.

Palestinian rescuers search for bodies in the rubble of destroyed houses in Gaza City. An Israeli warplane today blew up the house of a leading Hamas militant, killing at least 11 people, including the militant's wife and several children, Palestinian officials said.

The attack killed Salah Shehadeh, commander of the military wing of Hamas, known as Izzadine el-Qassam, the group said.

“Hamas mourns the hero, the leader, Salah Shehadeh,” a Hamas spokesman, Ismail Haniyeh, said in a statement. “Anyone who dreams of so-called peace is mistaken. There is nothing called ‘peace with Israel.”‘

Shehadeh’s wife and three of their children were among those killed in the air raid, Haniyeh said.

Shifa Hospital in Gaza City released a list of 11 dead, but it did not include the names of Shehadeh or any of his family, contributing to the confusion over how many were killed.

The hospital list included two babies, aged 2 months and 18 months, six children aged 3 to 11, and three adults.

In a statement, the Israeli military said that Shehadeh was behind “hundreds of terror attacks in the last two years against Israeli soldiers and civilians.”

Hamas threatened to strike back. “We will avenge the blood of the martyrs,” it said in a statement. The Palestinian Authority denounced the Israeli strike and called for international intervention to “stop these massacres.”

The Hamas military wing has claimed responsibility for dozens of attacks against Israelis during nearly two years of fighting, including many suicide bomb attacks. Also, Hamas has been behind almost daily mortar attacks on Jewish settlements in the Gaza Strip.

The air strike followed two Palestinian attacks last week that put an end to a monthlong respite in fatal Palestinian strikes against Israeli civilians, the longest such period since the current round of violence began in September 2000.

Nine Israelis were killed in a Palestinian ambush on a bus in the West Bank on July 16. The next day, two Palestinian suicide bombers blew themselves up in Tel Aviv, killing three bystanders.

In nearly 22 months of fighting, 1,779 people have been killed on the Palestinian side and 778 on the Israeli side.

On Monday, the two sides appeared to be moving toward easing months of tensions. Israeli Foreign Minister Shimon Peres had said the army was prepared to withdraw from two West Bank towns, Bethlehem and Hebron, as long as they remained quiet and if the Palestinians assumed control of security.

A top member of Hamas said the group was considering stopping suicide attacks if Israel withdraws; and an Israeli official said the government was looking into resuming security cooperation with the Palestinians after it pulls out.