Venice floods: Climate change behind highest tide in 50 years, says mayor
The highest water levels in the region in more than 50 years will leave "a permanent mark", Venice Mayor Luigi Brugnaro tweeted.
"Now the government must listen," he added. "These are the effects of climate change... the costs will be high."
The waters in Venice peaked at 1.87m (6ft), according to the tide monitoring centre. Only once since official records began in 1923 has the tide been higher, reaching 1.94m in 1966.
Images showed popular tourist sites left completely flooded and people wading through the streets as Venice was hit by a storm.
St Mark's Square - one of the lowest parts of the city - was one of the worst hit areas. St Mark's Basilica was flooded for the sixth time in 1,200 years, according to church records.
Pierpaolo Campostrini, a member of St Mark's council, said four of those floods had now occurred within the past 20 years. The city of Venice is made up of more than 100 islands inside a lagoon off the north-east coast of Italy.
Two people died on the island of Pellestrina, a thin strip of land that separates the lagoon from the Adriatic Sea.
A man was electrocuted as he tried to start a pump in his home and a second person was found dead elsewhere.
People throughout the city waded through the flood waters.
A number of businesses were affected. Chairs and tables were seen floating outside cafes and restaurants.
In shops, workers tried to move their stock away from the water to prevent any further damage.
One shopkeeper, who was not named, told Italy's public broadcaster Rai: "The city is on its knees."
A project to protect the city from flooding has been under way since 2003 but has been hit by soaring costs, scandals and delays.
The so-called Mose project - a series of large barriers or floodgates that would be raised from the seabed to shut off the lagoon in the event of rising sea levels and winter storms - was successfully tested for the first time in 2013.
The project has already cost billions of euros in investment. According to Italy's infrastructure ministry, the flood barriers will be handed over to the Venice city council at the end of 2021 following the "final phase" of testing.
Italy was hit by heavy rainfall on Tuesday with further bad weather forecast in the coming days. Venice suffers flooding on a yearly basis.
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