Storm Nils comes on the heels of three other episodes of extreme weather which caused severe flooding, claimed several lives and forced the evacuation of thousands of people in Spain and Portugal.

Gusts reached 105 kilometres per hour at Barcelona port, toppling trees and walls and prompting dozens of emergency calls, the Catalan civil protection agency said.

A total of 86 people required medical attention, with 34 taken to hospitals, the agency said. Among them, two remain in serious condition and one in critical condition.

At Barcelona's El Prat airport -- Spain's second busiest -- 101 flights were cancelled and 10 diverted, airport operator Aena said.

Some roads and rail lines were also disrupted.

The strong wind episode was "exceptional" for Barcelona and its metropolitan area, said the director of Catalonia's meteorological service, Sarai Sarroca.

Authorities in the region of around eight million residents suspended classes and non-urgent medical appointments, urging people to limit movement until Thursday evening when winds were expected to calm.

By reducing their travel, people helped prevent a higher number of accidents, the head of the region's interior department, Nuria Parlon, told a news conference.

The storm also hit parts of neighbouring Portugal and France.

In Portugal, flooding partially collapsed a highway viaduct between Lisbon and Porto when a river burst its banks.

The stretch of motorway had already been closed before it collapsed.

In southwestern France, a truck driver was killed by a falling tree and some 900,000 homes were without power.

Scientists say the increasing frequency and intensity of extreme weather events is due to climate change linked to rising greenhouse gas emissions.

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AENA