At least two people were killed in France and a landslide collapsed a stretch of elevated highway in Italy, leaving cars perched on a precipice, as heavy rains pounded the region over the weekend, trapping travellers, downing trees and triggering mudslides and floods in parts of both countries.

A 30-metre (100ft) section of highway along a viaduct near the flooded coastal city of Savona collapsed on Sunday. In an aerial video taken by firefighters, cars and one truck could be seen stopped perilously close to the point where the raised part of the A6 highway plunged on to a wooded area of the Liguria region.

A man from one of the cars closest to the precipice stood outside his vehicle, holding up his arms toward traffic to warn other drivers.

Giovanni Toti, the governor of Liguria, said a landslide caused the collapse in a muddy, hilly area. Firefighters were using dogs in the search for possible victims in the two-metre-high mud, he said. It was not known whether any vehicles might have plunged off the highway, which is supported by pillars at that point.

The road gave way about a mile outside Savona on the highway that links the city to Turin.

In 2018, 43 people died when a bridge collapsed in Genoa during a rainstorm.

Flooding in Turin, north-west Italy, prompted cancellation of a marathon. In France, Nice airport was closed briefly on Saturday. Rivers leading from the Alps to the French Riviera broke their banks, and sirens rang out in resort towns. Images on French media showed cars peeking above inundated streets and waves slamming on to roadsides.

One person died when a rescue boat sank while bringing three people to shore near the French town of Muy, the Var regional administration said. Another person was found dead in a car in the town of Cabasse.

French authorities were searching for two people missing in the floods, Christian Estrosi, the mayor of Nice said on Sunday.

In Italy, rescuers searched for a woman swept away by the surging Bormida river in the north.

There were rain-swollen rivers and flooded streets throughout Italy, where there has been heavy rainfall in much of the country for the past two weeks.

In Turin, the Po River overran its banks and flooded the medieval quarter and a popular riverside area known as the Murazzi.

One hundred and 50 people were evacuated from homes in Liguria, Italy’s hilly north-west coastal region. The region struggled with mudslides that blocked several roads, isolating hamlets. In Genoa, the region’s principal city, the neighbourhood of Boccadasse, a former fishing village with pastel-painted houses, was flooded after the sea rushed over retaining walls and on to the seaside road.

Venice was partially flooded, but the high tide’s level of nearly 1.3 metres in late morning was not unusual for the lagoon city accustomed to the phenomenon of acqua alta (high water). That level was nearly 60cm lower than the exceptionally high wind-driven tide that devastated the city earlier this month. Venetians and visitors walked on raised walkways through water that quickly receded.

Workers install walkways amid rising water levels at St Mark’s Square in Venice. Photograph: Andrea Merola/EPA

In parts of the south, cars attempted to drive through deep water and several motorists had to be rescued from their vehicles in flooded streets in Reggio Calabria in southern Italy, RAI state TV said.

In the Baroque city of Lecce in the heel of Italy, authorities ordered parks and cemeteries to be closed for fear that storm-battered trees might crash on to visitors, the Italian news agency Ansa said.

In addition to the two people who died in France, rescuers were searching for at least four others, the French interior minister, Christophe Castaner, said after visiting the area on Sunday. He said more than 1,600 people had been evacuated.

The French national weather service Meteo France said the area absorbed the equivalent of two months of average rainfall in 24 hours.