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Aid groups struggling to get food and medicine to Lebanese villages ravaged by Israeli airstrikes described harrowing journeys south on Tuesday, caught off-guard by increased air raids during a supposed 48-hour lull.

The violence slowed relief efforts by the United Nations, which had hastily planned additional convoys to take advantage of Israel's pledge to pause its aerial bombardment.

Israel denied access to two of the three U.N. convoys that planned to go south Tuesday. One made it to the southern port city of Tyre and was en route to Tibnine, where some 1,700 civilians were reported holed up in a hospital last week, with food and water supplies dwindling. Another reached Qana, where nearly 60 civilians died in a massive Israeli airstrike Sunday.

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Those who made the trip said it was dangerous.

"On the way out of town, the bombing started again. We stopped to see a bombed-out area on the edge of Marjayoun, but then we heard planes and bombing again," Mercy Corps spokeswoman Cassandra Nelson said by phone from a highway outside Marjayoun, a Christian town in the south. "At that point we got back in our cars and drove north as fast as we could."

Mercy Corps workers handed out blankets and food to some 2,000 people, mostly the elderly and families, in Marjayoun on Tuesday. It was the group's first aid shipment to south Lebanon.

While the U.N. and other international organizations apply for access to the war zone, Mercy Corps, an independent nonprofit group, notified Israel about its convoy Tuesday but did not wait for a response.

"If we wait for permission, we'll never get down here. We can't sit and wait for them to decide who gets to eat and who doesn't," Nelson said.

Humanitarian workers, many on their first trips south after three weeks of fighting, described seeing bodies on the roads.

"There were people that while they were fleeing, were killed, caught in the aerial bombardment," said Mona Hammam, the top U.N. humanitarian coordinator in Lebanon. It was unclear how long the bodies had been there.

Hammam said it was possible that some civilians had heard about the 48-hour pause and thought it was safe to emerge from bomb shelters, only to be hit by additional air raids.

"This 48-hour truce was essentially a chance for people to vacate their villages. We know there's been population movement away from the south. But under international law, that doesn't absolve the warring parties from their obligations to protect civilians," she said.

Sidon and Beirut received hundreds more refugees on Tuesday, she added.

Two U.N. convoys denied access to the south Tuesday would try again Wednesday to head to Naqoura and Rmeish, where the U.N. received reports of some 30,000 civilians holed up without food or water last week, Hammam said. No aid groups have been able to reach Rmeish so far, she said.

"We don't know what to anticipate when we get there," she said.

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