A third of Italy's precious cultural sites are in a state of emergency, campaigners are warning.

Venice, Pompeii and Rome are among the historic sites where pollution, tourism and illegal building are taking a heavy toll, according to environmental group Legambiente.

And in some places, ancient artefacts have been sold rather than protected, the group says.

"The threats range from polluted water to construction invading protected areas, but the main problem is knowing how to appreciate and take care of Italy's riches," said Federica Sacca, the group's art and culture campaigns representative.

The proliferation of illegal buildings growing up around Agrigento makes you think a bomb wouldn't be a bad solution

Unesco source

The group's pessimistic report comes after a study of all 36 Italian locations listed as world heritage sites by the United Nations.

The monuments, cities and sites are facing unprecedented threats, the group says.

Among the places it highlights are:

• Venice, where polluted water and heavy boat traffic are taking their toll on historic sites like St Mark's Square
• Pompeii, the great city destroyed by Mount Vesuvius in AD79, which is said to be under siege from illegal construction sites
• Agrigento in Sicily, where precious Greek temples are surrounded by buildings
• The Amalfi coast, where a rash of hotel construction has blighted the landscape

"Both funds and a change of attitude are needed, or some of these treasures could be lost forever," Ms Sacca said.

The UN body responsible for declaring the treasures as world heritage sites, Unesco, confirms that it has concerns over at least some of the locations, including Agrigento, where the ancient temples now stand surrounded by blocks of flats and hotels.

"The proliferation of illegal buildings growing up around Agrigento makes you think a bomb wouldn't be a bad solution," a Unesco source told the Reuters news agency.

The ruins of Pompeii are under threat

A Unesco spokesman said more cash would help, but insisted that most of the 36 sites were faring well.

"The care of sites is quite good, but Italy really should set aside more funds considering the size of its heritage," said Vincenzo Pellegrini.

Many other Italian historic sites, including churches and archaeological sites, are thought to be in graver danger, as they do not have the protection or publicity afforded to them by Unesco status.

It is "one of the great Italian paradoxes - the fortune of having a unique heritage of art, culture and history... and the inability to protect it," said Legambiente president Ermete Realacci.