They've struck at our most sacred inheritance. This is an affront to our ancestors

Archaeologist Federico Kaufmann Doig

The Inca citadel, 2,400 metres (7,782 feet) high in the Andes, was being used in the ad for Cusquena beer by US publicity firm J Walter Thompson when a crane smashed into a centuries-old granite sun clock.

The Intihuatana, or "hitching post for the sun", an integral part of the spectacular site which is protected by the UN and is visited by thousands of tourists every year, now has a gash as long as a ball-point pen.

Criminal charges, which carry a two-to-four-year prison sentence have been filed against the production company.

Federico Kaufmann Doig, a prestigious Peruvian archaeologist, said: "Machu Picchu is the heart of our archaeological heritage and the Intihuatana is the heart of Machu Picchu.

"They've struck at our most sacred inheritance.

"This is an affront to our ancestors."

Machu Picchu

Probably built and occupied from the mid-15th to the early or mid-16th century "Discovered" in 1911 by Yale University professor Hiram Bingham UNESCO World Heritage site since 1983

J Walter Thompson, the advertising agency contracted to shoot the advert for Cusquena beer, one of Peru's most popular brands, said it "deeply regretted" the accident.

"It was caused by a mechanical failure," said spokesman Alex Traugott, adding JWT had been making adverts for Cusquena's manufacturers Cervesur for 12 years and had shot other commercials at Machu Picchu.

Cervesur, one of the biggest companies in the impoverished Cuzco region, promised to help repair the damage, a procedure experts said would require advanced restoration techniques.

Criminal charges

Peru has sent restoration experts to Machu Picchu to assess the damage.

Machu Picchu, 2,400 metres high in the Andes

The shoot was approved by the National Institute of Culture's office at nearby Cuzco.

However, Gustavo Manrique, director of the office, said the permit specified only light equipment could be used.

Mr Manrique said the production crew sneaked the crane into the sanctuary at dawn after the National Institute of Culture specifically prohibited the use of a crane.