MILAN — Three-quarters of the lagoon city of Venice was under water Monday as large swathes of Italy continued to be battered by severe storms. At least 11 people were killed across the country over two days as a result of heavy rains and high winds, officials said Tuesday.

Tourists and residents of Venice donned high boots to navigate the city streets after strong winds raised the water level over 5 feet before receding. The water exceeded the raised walkways normally put out in flooded areas in Venice, forcing their removal. Transport officials closed the water bus system except to outlying islands because of the emergency.

Venice frequently floods when high winds push in water from the lagoon, but Monday's levels were exceptional. The peak level was the highest reached since December 2008, according to Venice statistics.

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Venice Mayor Luigi Brugnaro said a series of underwater barriers that are being erected in the lagoon would have prevented the inundation. The project, nicknamed Moses, is long overdue, beset by cost overruns and corruption scandals.

Brugnaro said he had asked to talk with Premier Giuseppe Conte to underline the urgency of the project, which would raise barriers when the tide reaches 43 inches. That happens, on average, four times a year in Venice.

Much of Italy is under alert for flooding from heavy rains, a problem exacerbated by a lack of maintenance of the country's many river beds. High winds toppled trees that killed passers-by in four incidents in Naples, Lazio and Liguria.

Officials closed major tourist attractions in Rome, including the Colosseum and Roman Forum, early because of heavy rains.

Veneto regional governor Luca Zaia says flooding this week could reach the levels of the 1966 flood that struck both Venice and Florence.