BAALBEK, Lebanon (Reuters) - An Israeli airstrike has destroyed an Ottoman-era building just a stone's throw from the UNESCO-listed temples of Baalbek in eastern Lebanon, the closest Israel has come yet to striking one of Lebanon's most treasured archaeological sites.

Heaps of grey masonry and twisted metal lay on Thursday next to a burnt-out bus just a few dozen metres (yards) from the World Heritage Site, a day after the attack which was part of a wave of strikes that killed 40 people in and around the city.

The Israeli military has told residents of the entire city to leave Baalbek, in Lebanon's eastern Bekaa Valley, which houses one of the biggest and best preserved complexes of Greco-Roman and Phoenician temples in the Levant.

The surrounding city has come under repeated attack from Israel which says leaders of the Iran-backed Shi'ite movement Hezbollah shelter there.

Governor Bachir Khodr told Reuters the destroyed building in the historic Manshiyeh neighbourhood just outside the ancient temple site was valuable in itself, dating to the Ottoman era.

"It's a very artisanal neighbourhood, typically full of tourists. There was no one in that building," he said.

No damage was immediately visible to the temple complex, but it was too early to be conclusive, he said.

"The castle guards visually confirmed there was no damage but we need experts - engineers and archaeologists - to come look. No one has been able to do so yet because of the strikes," Khodr said.

Maya Halabi of the Baalbek International Festival said that a total of three Ottoman-era sites had now been damaged by Israeli strikes in recent weeks, including the Gouroud Barracks, the Palmyra Hotel and the house destroyed on Wednesday.

"The Acropolis - where the temples are - is just a few meters away. They haven't been damaged yet and we hope that won't happen," Halabi told Reuters.

Israel launched a ground assault and massive air campaign against Hezbollah in late September after a year of exchanging fire across the border in parallel with the Gaza war.

More than 3,000 people have been killed in Israeli strikes on Lebanon over the last year, the vast majority in the past six weeks.

(Reporting by Maya Gebeily; Editing by Peter Graff)