Swathes of Spain and Portugal were on high alert on Thursday as heavy rain and strong winds battered the Iberian peninsula, felling trees, disrupting transport and forcing the closure of schools in some areas.

One person was in a serious condition after being struck by a falling tree in the northeastern Spanish region of Catalonia in the latest storms to hit the region in the past few weeks.

Part of the A1 motorway between Portugal’s north and south collapsed on Wednesday night near the medieval city of Coimbra after a levee broke underneath.

A red alert - the highest level - has been decreed in the northern Spanish regions of Galicia, Cantabria and the Basque Country after the arrival on Wednesday of Nils, the eighth storm to hit Spain this year.

Weather agency AEMET warned of waves up to nine metres (30 feet) tall.

Authorities in Catalonia suspended classes and sporting events and restricted non-essential healthcare services as wind gusts of over 105 km per hour (65 mph) felled trees, disrupting road and rail traffic across the region.

At least five people - including the person who was in serious condition after being hit by a tree - have been injured in the winds in Catalonia, Nuria Parlon, the head of the region’s interior department, told radio station RAC1.

Catalan civil protection services sent a mobile emergency alert warning the population to stay indoors and avoid unnecessary travel.

At least 40 flights departing from or landing at Barcelona’s El Prat airport have been cancelled, sources at airport operator Aena told Reuters. The airport remained operational, but with restrictions that could cause further delays and cancellations, they said.

In Portugal, a weather phenomenon known as an “atmospheric river” - a wide corridor of concentrated water vapour carrying massive amounts of moisture from the tropics - brought new downpours, affecting the north to a greater extent, where authorities have evacuated about 3,000 residents.

The Portuguese Institute of the Sea and the Atmosphere (IPMA) said Storm Oriana - a separate Atlantic depression approaching the north of the peninsula - would not directly affect mainland Portugal, but would cause heavy rainfall and wind across most of the country on Thursday and Friday.

Infrastructure Minister Miguel Pinto Luz told reporters that restoring the affected stretch of the A1 motorway would take weeks, as repairs needed to wait for the floodwaters to recede.

The situation in Coimbra was stable overnight, and there was no need to conduct additional evacuations, state news agency Lusa reported on Thursday, citing a source in the local civil protection service.