Italian firefighters used a helicopter to ferry 17 people to safety from the French town of Vievola, including a woman with two grandchildren.

A bulldozer fetched another eight people who managed to climb the Col de Tende, a high mountain pass linking France and Italy, to a tunnel.

Fifteen people were stuck in a train station overnight and eight more remained missing in France.

Storm Alex barrelled into France’s west coast on Thursday bringing powerful winds and rain across the country before moving into Italy, where torrential rain of up to 50 centimetres and high winds crashed into the border area.

The storm caused major flooding on both sides of the border, destroying bridges, blocking roads and cutting off communities.

A volunteer firefighter died in Italy’s Aosta Valley during a rescue operation and a search team found a body in the Piedmont region’s Vercelli province, where a man had been swept away by flood waters late on Friday.

The presidents of Italy’s Piedmont and Liguria regions signed a joint letter calling on the government to declare a state of emergency with several villages cut off.

“The situation is very serious. It is like it was in 1994,” when 70 people died after the Po and Tarano rivers flooded, Piedmont’s president, Alberto Cirio, told La Stampa newspaper.

“The difference being 630 millimetres of water fell in 24 hours – unprecedented in such a small timeframe since 1954.”

Cirio added that Italy was already struggling to cope with the effects of the coronavirus pandemic, which has left some 36,000 dead and shattered the economy over the past six months.

“We are already in an extraordinary situation,” he said.

“Because of the pandemic the region will this year receive €200 million less in tax receipts.

“If the state does not intervene [with rescue funding] we shall not recover.”

Authorities in Venice expected the city to be submerged by an “acqua alta”, an occasional tidal peak coming in from the Adriatic to reach the lagoon city and flood as far as the iconic Saint Mark’s Square.

But flooding was prevented by the long-delayed and controversial Mose flood barrier system, which was activated for the first time on Saturday.

People look at the yellow flood barriers being raised in Venice, on October 3, 2020. (Photo: AAP)

“Today, everything is dry. We stopped the sea,” Venice Mayor Luigi Brugnaro told reporters after raising a glass in celebration with some of the engineers and officials responsible for the multi-billion euro project.

The network of 78 bright yellow barriers that guard the entrance to the delicate Venetian lagoon lifted from the sea bed as the tide, driven by strong winds and rain, started to climb.

The system of flood defences is one of the biggest civil engineering projects in the world.