JERUSALEM — Israeli jets struck three sites in Gaza on Monday after a rocket was launched at Israel, the military said, disrupting a relative lull in the war-torn territory at the start of a major Muslim holiday.

The airstrikes followed an almost 12-hour pause in the fighting and came as international efforts intensified to end the three-week war between Israel and Hamas.

The U.N. on Monday called for an "immediate" cease-fire in the fighting. On Sunday, President Barak Obama telephoned Israeli Prime Minister Benjamin Netanyahu to push for an immediate end to the conflict.

Israel's military said it struck two rocket launchers and a rocket manufacturing facility in central and northern Gaza after a rocket hit southern Israel earlier in the day.

The Israeli military also said it dropped leaflets over Gaza City on Monday afternoon, warning Palestinian residents in the coastal strip that Israel "will not tolerate any attempt to harm Israeli civilians, and the consequences will be severe."

Earlier, the military said troops on the ground were pressing on with efforts to destroy the cross-border tunnels constructed by Hamas for attacks inside Israel. Also, the military opened artillery fire on Beit Lahiya in northern Gaza in response to the rocket fired at Ashkelon, said the office of Israel's military spokesman.

The military said eight rockets had been fired from Gaza at Israel since midnight Sunday.

In New York, an emergency meeting of the U.N. Security Council called for "an immediate and unconditional humanitarian cease-fire." And while it was the council's strongest statement yet on the Gaza war, it was not a resolution and therefore not binding.

Palestinian U.N. Ambassador Riyad Mansour did not hide his disappointment.

He said the council should have adopted a strong and legally binding resolution a long time ago demanding an immediate halt to Israel's "aggression," providing the Palestinian people with protection and lifting the siege in the Gaza Strip so goods and people can move freely.

"You cannot keep 1.8 million Palestinian civilians in the Gaza Strip in this huge prison," Mansour told reporters. "That is a recipe for disaster. It is inhumane, and it has to be stopped and it has to be lifted."

Israeli U.N. ambassador Ron Prosor also criticized the statement, saying it lacked balance because it didn't mention Hamas, the firing of rockets into Israel or Israel's right to defend itself.

Israel started its Gaza operation on July 8 to stop the rocket fire from the coastal territory and intensified it on July 17 to neutralize Hamas cross-border tunnels built to carry out attacks on Israeli territory.

The pressure for a cease-fire followed new attacks launched by Israel and Hamas on Sunday despite the back-and-forth over proposals for another temporary halt to the fighting. The Security Council urged Israel and Hamas "to accept and fully implement the humanitarian cease-fire into the Eid period and beyond." It said this would allow for the delivery of urgently needed assistance.

The council's presidential statement also called on the parties "to engage in efforts to achieve a durable and fully respected cease-fire, based on the Egyptian initiative."

Obama telephoned Netanyahu on Sunday to express his concern over the mounting Palestinian casualties.

The White House said Obama reiterated that Israel has a right to defend itself and condemned Hamas' rocket attacks. Obama said a lasting peace will ultimately require a demilitarized Gaza and dismantling of terror groups. The U.S. president also pushed for an immediate, unconditional cease-fire that would allow Israeli and Palestinian civilians to return to normalcy.