When the five-tonne news kiosk that he had worked in for 25 years began to float away, Walter Mutti realised that this was no ordinary Venice flood.

The storm surge overwhelmed his spot alongside the Giudecca canal on Tuesday night as swiftly as it inundated much of the rest of the city and its many cultural treasures.

“At 9.45pm there was no wind, then all of a sudden it started howling and the water rose 10 inches in 20 minutes,” Mr Mutti, 50, said. Fearing he would be trapped in his supposedly flood-proof kiosk, he knew he had to act fast. “As the kiosk started dancing around I scrambled out to save myself and headed home, only to return at 2am to find it had vanished.”

He was one of thousands of people caught out by Venice’s worst flood in more than 50 years. A high tide and 60mph winds pushed the water levels to 74 inches above normal on Tuesday — just short of the 1996 record of 76 inches. The water swamped homes, damaging priceless buildings and artefacts, and tore gondolas from their moorings. St Mark’s Square, the heart of the city, was chest-deep in parts, and tourists posted pictures online of water cascading through the doors to their hotels.

Last night the flood warning sirens sounded again as the waters rose anew, and another dangerous tide was forecast for today.

Giuseppe Conte, the prime minister, described the disaster as “a blow to the heart of our country”. Last night he declared a state of emergency and promised €20 million in immediate aid.

St Mark’s Square, the heart of the city, was chest-deep in parts.

Repairs will cost hundreds of millions of euros, according to Luigi Brugnaro, the mayor. He laid the blame squarely on climate change and the “tropicalisation” of Mediterranean weather.

The city’s gondoliers were not spared as the floodwaters rose.

Old books at the famous Acqua Alta di Venezia bookstore were completely submerged.

“Gondolas were smashed against their wooden jetties, which splintered and were swept away, others were thrown on to dry land — we are looking at a €500,000 bill for repairs,” Aldo Reato, a former head of the Venice gondoliers’ association, said.

Andrea Balbi, the current head, said that 17 of the gondolas, which are hand-made by local artisans and cost up to €35,000 each, were torn from their moorings and hurled ashore close to St Mark’s Square. A total of 80 of the city’s 433 gondolas were damaged.

“They will take for ever to be fixed due to the dwindling number of traditional gondola builders left in Venice,” Mr Reato said.

With more storms expected today, water levels are predicted to be at 63 inches above normal levels.

“Gondolas were smashed against their wooden jetties, which splintered and were swept away, others were thrown on to dry land.”

Christian Costantini, the regional head of the Carabinieri police heritage protection squad, warned Venice’s museums to batten down the hatches yesterday. “I have never seen anything like this,” he added.

The flooding is the result of an unusual combination of tides and fierce winds.

Tourists in St Mark’s Square took advantage of a short spell of sunshine yesterday to snap selfies of themselves in their galoshes, while shopkeepers used the respite to mop out their premises and recount the ordeal they faced on Tuesday.

“The water came up to the third shelf,” said Sofia, manager of a hardware store near the square. “That beats last year, when it also flooded but then it only reached the second shelf. At least we are selling out of wellington boots.”

High waters are routine in Venice, forcing residents and tourists alike to walk on wooden platforms erected along the submerged streets, but experts say serious flooding is becoming ever more frequent. They claim the increase is due to waters around the city rising 14 inches in the past 150 years, partly due to warming oceans but also because the city has sunk after massive amounts of groundwater were pumped out to serve factories on the mainland.

“At least we are selling out of wellington boots.”

Weather experts at the Italian National Research Council use a forecasting system with up to 40 variables they refer to as the “spaghetti” chart, due to its complexity. Many locals blame extreme weather. Barbara Pastor, an architect, said her house had been inundated with “black, stinking” water on Tuesday. “It is the first time water ever entered my house, and now the fear is it can happen any time thanks to these freak winds that climate change has brought,” she said.

Other homeowners found water gushing from their toilets like fountains or cascading from electricity sockets as canal water surged up through the city’s drains.

At the famed St Mark’s basilica, where the floodwater broke windows and submerged the crypt under more than 3 feet of water, Giuseppe Maneschi, the manager, watched as staff mopped the site’s precious mosaics with fresh water to remove salt left by sea water. “The salt is the enemy. It gets into the bricks and the marble and cracks them,” he said. The ancient church flooded on Tuesday and again yesterday.

Italian director Federico Fellini and his wife, actress Giulietta Masina, at the 1955 Venice Film Festival.

Water could be seen spiralling down a drain near the entrance like a draining bathtub, back into the city’s sewers, as the tide receded.

“It’s far from over. This part of the church will be filling up again tonight,” Mr Maneschi said.

“The fear is it can happen any time thanks to these freak winds that climate change has brought.”

Residents have become accustomed to listening for the city’s network of sirens, which warn them of impending high water. One prolonged tone means that the water is expected to peak at 43 inches; two differing tones mean 47 inches is forecast, and so on, up to 55 inches.

“The problem is that it stops there — as if they haven’t got round to realising it is now going far higher,” one resident said.

There were widespread demands yesterday for progress on the Mose flood barrier planned for the mouth of the Venice lagoon. Work has been held up for years amid corruption scandals, with allegations that as much as €40 million has been lost to kickbacks for politicians. The barrier is now due to open in 2021.

Arrigo Cipriani, the owner of Harry’s Bar, a renowned Venice drinking spot, said the Mose flood barrier project had prompted “the biggest thievery in the last 50 years.” He added: “It is thanks to previous and current governments that it has not been activated.”