Venice could lose its status as a World Heritage Site if it does not adequately protect itself from worsening flooding, UNESCO representatives have warned as they offered help after recent inundations.

"Key buildings which are within the World Heritage area are threatened. ... This is of great concern to us, especially as this is not a single incident," said Mechtild Roessler, director of the World Heritage Center.

Venice suffered heavy damage when floodwaters reached one of the highest levels in more than 50 years this month.