Venice’s mayor has called the city a disaster zone after the second-highest tide ever recorded swept through it overnight, flooding its famous basilica and leaving many squares and alleyways deep under water.

The worst flooding in the Italian city in more than 50 years prompted calls on Wednesday to better protect the historic city from rising sea levels as officials calculated hundreds of millions of euros in damages.

“Venice is on its knees,” Mayor Luigi Brugnaro said on Twitter. “St. Mark’s Basilica has sustained serious damage, like the entire city and its islands.”

Night-time footage showed a torrent of water whipped up by high winds raging through the city centre while Luca Zaia, governor of the Veneto region, described a scene of “apocalyptic devastation”.

The exceptionally intense “acqua alta”, or high water, peaked at 1.87 metres (six feet) late on Tuesday, forcing stranded tourists to wade through rapidly rising waters in the dark in search of safety as the flood alarm rang out.

Only once since records began in 1923 has the water crept even higher, reaching 1.94 metres in 1966.

Brugnaro said the situation was dramatic. “We ask the government to help us. The cost will be high. This is the result of climate change,” he said on Twitter.

A flood barrier was designed in 1984 to protect Venice from the kind of high tides that hit the city on Tuesday, but the multibillion-euro project, known as Mose, has been plagued by corruption scandals and is still not operative.