Water levels rose above 140 centimeters overnight and were expected to remain above critical levels "for about 15 hours," local authorities said.

It was the highest tide level since December 2010.

Venice starts flooding when waters rise about 110 centimeters. When the 140-centimeter mark is reached, 58 per cent of the city is under water.

On Thursday, the famous St Mark Square was 60 centimeters under water. Tide levels were expected to return to more normal levels on Friday.

Chioggia, a town on the southern edge of the Venice lagoon, was the worst hit. Tides there reached a peak of 164 centimeters, the third-highest level since 1966, when the area was devastated by a huge flood.

Venice, which is built on hundreds of small islands, often experiences high water in autumn and winter causing floods to the city's narrow alleyways and squares, including the famous St Mark's.

To tackle the problem, Italian authorities are building a complicated dam system, the MOSE, which is meant to insulate the city

from tide levels above 110 centimeters.

But MOSE has been beset by cost overruns, delays, and opposition from environmental groups. The project is now expected to cost over 6 billion euros ($7.8 billion) and become fully operational in 2016.