Thousands of Palestinians attended the funerals on Saturday of three senior Hamas militants killed by Israel in an overnight airstrike in southern Gaza, and Hamas leaders warned that Israel would bear the consequences.

But the area remained calm on Saturday, and Hamas, the Islamic group that controls Gaza, seemed wary of fueling a new round of hostilities.

The Israeli strike early Saturday came a week after the armed Palestinian groups in Gaza reaffirmed their commitment to an unofficial cease-fire with Israel. The agreement ended 10 days of heavy rocket and mortar fire from Gaza against southern Israel, repeated Israeli airstrikes in Gaza and fears of an escalation into all-out confrontation.

Only one armed group, the Popular Resistance Committees, a small faction loyal to Hamas, announced Saturday that it was withdrawing from the cease-fire. “We are free from the decision of not escalating with Israel,” said Abu Mujahed, a spokesman for the group. “Our response will be at the same level of the crime.”

The Israeli military said that the three militants were members of a Hamas terrorist squad planning to kidnap Israelis over the Passover holiday in Israel and in the resorts of the Egyptian Sinai.

The Hamas military wing confirmed that the three were Hamas fighters but denied the plot. Citing the Israeli reference to Sinai, it said, “We only operate within the borders of historic Palestine.” It added that the dead had been responsible for producing and developing weaponry.

Ismail Haniya, the head of Hamas’s government in the Palestinian coastal enclave, attended the funerals on Saturday with representatives of other Palestinian factions. Fawzi Barhoum, a Hamas spokesman, described the airstrike on a car carrying the militants as “a crime and a systematic continuation of murder, criminality and state terrorism.”

“The Israeli government,” he added, “shoulders the responsibility for the consequences."

Last weekend, Hamas met with the Gaza groups and persuaded them to reinstate the unofficial cease-fire with Israel. Since then, the Israeli military killed three militants from the Islamic Jihad movement in two airstrikes. Israel said the militants were responsible for firing rockets at Israel. Israel fought a three-week offensive against Hamas in Gaza in 2008-9 as a response to years of rocket fire.