A Hezbollah minister in Lebanon's Cabinet denies any involvement by the militant group in the firing of rockets from Lebanon into Israel.

At least three rockets were fired Thursday, and Israel responded with a few artillery shells into Lebanon, which borders the country to the north. The exchange threatened to open a second front as Israel continues its offensive against the militant group Hamas on its southern border, in the Gaza Strip.

Two people were lightly injured, and the rockets that exploded in Israel's north raised the specter of renewed hostilities with Hezbollah, just 2 1/2 years after Israel battled the guerrilla group to a 34-day stalemate. Hezbollah started the 2006 war as Israel was battling Palestinian militants in Gaza.

No group claimed responsibility and Lebanon's government, wary of conflict, quickly condemned the rocket fire. But Hezbollah has been suspected in the past by Israel and its opponents in Lebanon of using allied radical groups to irritate Israel with a lower risk of retaliation.

Israel now faces threats on two of its borders from Islamic organizations with close ties to Iran. Hamas rockets threaten about 1 million Israelis in the south out of a population of 7 million, and Israel's military believes that the rockets in the Hezbollah's arsenal can hit most of the remaining 6 million.

For a second straight day, Israel said it suspended is Gaza military operation for three hours to allow in humanitarian supplies, but a United Nations aid agency told Reuters it has suspended its Gaza operations because of the risk posed by Israeli forces.

A U.N. official said Israeli forces fired on a truck on a U.N. aid mission and killed the driver. U.N. spokesman Adnan Abu Hasna says the incident took place during the lull declared by Israel.

He says the U.N. coordinated the delivery with Israel, and the vehicle and was marked with a U.N. flag and insignia when it was shot in northern Gaza.

The Israeli army said it was investigating.

Click to view photos from the conflict.

Before the lull on Thursday, Israel killed at least 11 people in Gaza, including five militants, raising the death toll from its 13-day offensive to 699 people, according to Palestinian medical officials. 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. There was a serious blast," said Henry Carmelli, the home's manager.

About three hours later, air-raid sirens went off again. But authorities said it was a false alarm.

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 on Dec. 27. 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. 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 continues.

An Israeli Cabinet minister, Meir Sheetrit, suggested that Lebanese splinter groups, not Hezbollah, were responsible. He said the government had no interest in renewing hostilities.

"Even though we have the ability to respond with great force, the response needs to be carefully considered and responsible," Sheetrit told Army Radio. "We don't need to play into their hands."

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.

Nine 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.

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" and would not be enough 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.

Of the Palestinians killed since Dec. 27, some 350 were civilians, among them 130 children, according to Palestinian medical officials. Eleven Israelis have been killed, including three civilians, since the offensive began. The army said Thursday that an infantry officer was killed by an anti-tank missile.

Growing international outrage over the human toll of Israel's offensive, which includes 3,000 Palestinians wounded — could work against continued fighting. So could President Bush's departure from office this month and a Feb. 10 election in Israel.

But Israel has a big interest in inflicting as much damage as possible on Hamas, both to stop militant rocket fire on southern Israeli towns and to diminish the group's ability to play a spoiler role in peace talks with Palestinian moderates.

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.

Hamas, a militant Islamic group which the U.S. and Israel consider a terrorist organization, wrestled control of Gaza from the Palestinian Authority in June 2007, and since 2001, has launched more than 3,000 Qassam rockets and 2,500 mortar attacks against Israeli targets.

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.

The Israeli Cabinet formally decided on Wednesday to push ahead with the offensive while at the same time pursuing the cease-fire.

The military has called up thousands of reserve troops that it could use to expand the Gaza offensive. Defense officials said the troops could be ready for action by Friday.

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 Zaytun neighborhood of Gaza City on Wednesday.

A Red Cross spokesman said 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 Associated Press contributed to this report.