The United Nations says it is halting all aid deliveries to the besieged Gaza Strip. It is citing a series of Israeli attacks on U.N. staff and installations.

The announcement came shortly after the driver of a U.N. truck was killed by tank fire as he was headed to an Israeli border crossing to pick up an aid shipment.

The U.N. said the delivery had been coordinated with Israel. The Israeli army has not commented.

Spokesman Chris Gunness says aid shipments are being suspended until the safety of U.N. staff can be guaranteed.

Earlier this week, nearly 40 people were killed by Israeli mortar fire outside a U.N. school. Israel said its troops had come under fire by militants using the building for cover.

THIS IS A BREAKING NEWS UPDATE. Check back soon for further information. AP's earlier story is below.

JERUSALEM (AP) _ Militants in Lebanon fired at least three rockets into Israel early Thursday, threatening to open a new front for the Jewish state as it pushed forward with a bloody offensive in the Gaza Strip that has killed nearly 700 people. Israel responded with mortar shells.

The rockets raised the specter of renewed hostilities on Israel's northern frontier, just 2 1/2 years after Israel battled the Hezbollah guerrilla group to a 34-day stalemate. War broke out between Hezbollah and Israel in 2006 as Israel battled Palestinian militants in Gaza, on Israel's southern borders.

No group claimed responsibility. Lebanon's government condemned the attack, and Hezbollah _ which now plays an integral role in Lebanon's government _ denied any responsibility for the rocket fire, which lightly injured two Israelis.

For a second straight day, Israel said it suspended is Gaza military operation for three hours to allow in humanitarian supplies. Shortly before the pause took effect, however, the U.N. said one of its aid trucks came under Israeli fire, killing the driver.

U.N. spokesman Adnan Abu Hasna said the U.N. coordinated the delivery with Israel, and the vehicle was marked with a U.N. flag and insignia when it was shot in northern Gaza. The Israeli army said it was investigating.

The allegation was sure to raise tensions with the United Nations, which has already demanded an investigation into Israel's shelling of a U.N. school in Gaza that killed nearly 40 people. At the time, Israel said it opened fire after militants hiding in the crowd shot mortar shells at Israeli troops.

In new Gaza violence, Israel killed at least 11 people, including three who were fleeing their homes, raising the death toll from its 13-day offensive to 699 Palestinians, according to Palestinian medical officials. Eleven Israelis have died since the offensive began Dec. 27.

The offensive is meant to halt years of Palestinian rocket attacks on southern Israel, but with roughly half the dead believed to be civilians, international efforts to broker a cease-fire have been gaining steam.

One of the Lebanese rockets went through the roof of a retirement home in Nahariya, about five miles from the border, and exploded in the kitchen as some 25 residents were eating breakfast in the adjacent dining hall. One resident suffered a broken leg, another bruises, apparently from slipping on the floor after emergency sprinklers came on.

"The rocket entered through the roof, hurling the water heaters into the air. It went through bedrooms upstairs and then into the kitchen," said Henry Carmelli, the home's manager.

Israel has repeatedly said it was prepared for a possible attack on the north since it launched its bruising campaign against Hamas militants in Gaza, to the south. Israel has mobilized thousands of reserve troops for such a scenario, and leaders have warned Hezbollah of dire consequences if it enters the fighting.

"We are following what is happening in the north. We are prepared and will respond as necessary," Defense Minister Ehud Barak told reporters.

Lebanese Prime Minister Fuad Saniora condemned both the attacks and Israel's retaliatory fire. The attacks are "the work of parties who stand to lose from the continued stability in Lebanon," Saniora said.

Hezbollah has said it does not want to draw Lebanon into a new war and Lebanese Labor Minister Mohammed Fneish, a Hezbollah representative in the Cabinet, told The Associated Press the militant group was not aware of the rockets targeting Israel.

Small Palestinian groups, who have rocketed Israel twice since the end of the 2006 war, have recently threatened to open a new front against Israel if the fighting in Gaza continued.

Cabinet Minister Isaac Herzog welcomed the Lebanese government's condemnation of the attack.

"We look at it as a local event, something that was predictable," he said.

Herzog said Israel welcomes the Egyptian-French diplomatic activity, but said the government was prepared to "deepen" its offensive if the peace efforts fail.

Shortly after the first rockets fell around the town of Nahariya, five miles south of the Lebanese border, Lebanese TV stations reported Israeli mortar fire on open areas in southern Lebanon. The Israeli military confirmed it carried out "pinpoint fire" in response without elaborating.

Israeli defense commentators said they expected the rocket fire to be a one-time show of solidarity with the Palestinians, not a declaration of war. Still, police said public bomb shelters throughout the north were opened.

Palestinians reported some two dozen airstrikes in Gaza on Thursday. One militant was killed and 10 wounded in Gaza City, while an airstrike in northern Gaza killed three members of a rocket-launching cell, Palestinian medical officials said. The attack took place about 150 yards from a hospital and wounded 12 bystanders. The Israeli army has repeatedly said militants use civilian areas for cover.

Seven other Palestinians were killed in separate incidents, including three civilians _ en elderly man and two women _ who were fleeing their homes in northern Gaza, officials said.

In Geneva, the international Red Cross said it found four small children alive next to their mothers' bodies in the rubble of a Gaza home hit by Israeli shelling. The neutral aid group says a total of 15 dead were recovered from two houses in the Zeitoun neighborhood of Gaza City on Wednesday.

A Red Cross spokesman says rescuers had been refused permission by Israeli forces to reach the site for four days. It said the delay in allowing rescue services access was "unacceptable."

The Israeli offensive has reduced Palestinian rocket fire, but not stopped it altogether. Several barrages were reported Thursday, including one strike that damaged a school and sports center in the southern city of Ashkelon, police said. Both buildings were empty.

For a second day, Israel's Defense Ministry said the offensive was halted for three hours to allow Gaza residents to stock up on supplies and to allow aid shipments into the besieged area. Ministry spokesman Peter Lerner also said some 300 Palestinian holders of foreign passports would be allowed to leave.

The lull appears to be in response to international pressure on Israel to try relieve civilian suffering in Gaza. U.N. spokesman Chris Gunness said three hours was "wholly inadequate" to relieve widespread food and water shortages.

After Wednesday's lull, Israel quickly resumed its offensive, bombing suspected smuggling tunnels near the border with Egypt after Hamas responded with a rocket barrage. Israeli planes destroyed at least 16 empty houses.

The tunnels are Hamas' lifeline, used to bring in arms, money and basic goods. Israel says local homes are used to conceal the tunnels.

Despite the heavy fighting, strides appeared to be made on the diplomatic front with Secretary of State Condoleezza Rice saying the U.S. supported a deal being brokered by France and Egypt.

While the U.N. Security Council failed to reach agreement on a cease-fire resolution, Egypt's U.N. Ambassador Maged Abdelaziz said representatives of Israel, Hamas and the Palestinian Authority agreed to meet separately with Egyptian officials in Cairo.

Israeli envoys arrived in Egypt on Thursday to discuss the proposal.

For Israel to accept a proposed cease-fire deal, "there has to be a total and complete cessation of all hostile fire from Gaza into Israel, and ... we have to see an arms embargo on Hamas that will receive international support," said government spokesman Mark Regev.

For its part, Hamas said it would not accept a truce deal unless it includes an end to the Israeli blockade of Gaza _ something Israel says it is not willing to do. Israel and Egypt have maintained a stiff economic embargo on Gaza since the Hamas takeover.

The Palestinian Authority controls the West Bank while Hamas rules Gaza _ two territories on opposite sides of Israel that are supposed to make up a future Palestinian state. Hamas took control of Gaza from forces loyal to Palestinian Authority President Mahmoud Abbas in June 2007.

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Weizman reported from Jerusalem and Barzak from Gaza City. Associated Press writer Sam F. Ghattas contributed to this report from Beirut, Lebanon.