Three UNESCO World Heritage sites in Lebanon, including some of the Middle East's most significant ancient ruins, are in urgent need of repairs after a month of fighting between Israel and Hezbollah, the U.N. agency said Monday.

In one case, frescos in a Roman-era tomb in Tyre were shaken to the ground when a building 500 feet away was bombed, said U.N. experts, who visited Lebanon and reported on their findings. Some of the paintings were destroyed.

In the ancient Phoenician city of Byblos, ruins were stained by an oil spill. In Baalbek, another Phoenician city which has some of the finest examples of imperial Roman architecture temples may have suffered structural damage, the experts said.

"Although it was not directly hit and did not suffer any major visible damage, cracks in the stone were probably widened by the shaking caused by nearby bombings," said Mounir Bouchenaki, who headed the mission.

Bouchenaki added that further investigations, using sophisticated photographic measurement technology, would be needed to determine the extent to which Baalbek's colossal structures were damaged.

Byblos grappled with a massive oil spill caused by the bombing of a power plant in mid-July. It has been described as Lebanon's worst environmental disaster, and UNESCO said Byblos was the most seriously damaged of the heritage sites.

"While the Lebanese army had in large part cleaned up the oil spill before our arrival, the Heritage-listed site was directly affected," Bouchenaki said. "The stones of the two ancient towers at the port's entrance, and all the archaeological ruins, are very stained. The site is in immediate danger."

Bouchenaki warned that the site would have to be cleaned before winter to prevent permanent devastation.

"These stones can't be cleaned mechanically," he said. "The cleanup will have to happen manually, with brushes and specially formulated detergents."

He said it would take 25 people up to 10 weeks to complete the cleanup, and that they would need a week of training first. The operation in Byblos was expected to cost around $100,000, he said.

Most of Lebanon's heritage remained intact during the fighting, the experts said. Lebanon has six World Heritage sites in all. The other three are the city of Anjar, the Holy Valley and the Forest of the Cedars of the Gods.

Francoise Riviere, the assistant director-general of UNESCO's cultural branch, said repairing cultural treasures could have psychological benefits in a country proud of its history.

"We want to use culture to heal the trauma which was felt, especially by the children of south Lebanon who survived the war," she said. "It is something we experienced after the tsunami in Indonesia — culture can give meaning to those who have lost everything."