Much of the Italian lagoon city of Venice was engulfed with water after high tides and strong winds caused the most severe flooding for years.
"A strong low-pressure system is spinning through southern Europe, spreading heavy rain and strong winds across northern Italy", said weather.com meteorologist Chris Dolce.
Venice, which is famous for its canals, is frequently overwhelmed by water in the period from October to December, but the recent flooding has seriously affected the area. That happens, on average, four times a year in Venice.
The wooden floors in the almost 300-year-old Florian cafe nearby also received serious damage.
Roads remain blocked and rain links destroyed, leaving towns isolated as residents fear for their lives.
In Italy, where Venice was inundated by near-record flooding and ferocious storms drove high winds reaching up to 180kmh, authorities announced a further six deaths, after confirming five people had died on Monday.
Portofino, where the family of former prime minister Silvio Berluscon live, remains isolated after a landslide blocked the town connecting to Santamaria Ligure. "We had a sort of tsunami, eight-meter waves".
Two young people died south of Rome when a tree hit their auto while another was killed when high winds toppled slender pine trees in the nearby town of Terracina.
News agency Ansa reported damage to the mosaic floors inside Venice's famed St Mark's Basilica, where waters reached 90cm.
Italian media reported that around 170 people, tourists and hotel staff, were stranded by heavy snowfall at the Stelvio Pass on the Swiss border.
"It was the flawless storm during which adverse meteorological conditions contributed to the situation in the sea and winds", civil protection chief Angelo Borrelli said.
A young man was killed by a falling tree in the middle of the street in the Naples area, according to the authorities, while an elderly person died after falling from a piece of cornice in the north-west, near Savona.