Four people have been confirmed dead in Spain after Storm Gloria swept into Catalonia and left a trail of destruction along the Valencia coastline.

The dead include a man, 63, who was killed in his home in the province of Ávila after being hit by flying roof tiles and a 54-year-old homeless woman who froze to death near Valencia.

The storm brought wind gusts of over 100km/h, snow, freezing rain and massive waves.

Giant waves were seen breaking over sea walls at the Port Olímpic in Barcelona and washing onto the promenade.

Four people are still thought to be missing.

They include a 25-year-old British man who went missing yesterday while on a beach in the north of the holiday island of Ibiza in the Mediterranean Sea.

30 provinces were issued with weather alerts, with red alerts in place for Spain's northeastern region.

Gloria dumped over 100 litres of rain per square metre as it swept into Catalonia.

In Girona province, more than 200,000 residents were left without power after the storm downed a power cable.

Spanish national weather agency Aemet said the storm is starting to abate, although it has kept Catalonia and the Balearic Islands on alert.

The worst of the conditions have moved into southern France where one forecaster told local media that Gloria was the worst storm in the region since 1982.