A family of three are among those who have died since the unprecedented blackout in Spain and Portugal. Police said a married couple and their son were found dead at their three-storey home in Taboadela, a town of less than 1,500 in Galicia, northeast Spain.

They were found by a care worker next to a domestic generator used by one of the victims to power an oxygen machine. The father, 81, his wife, 77, and their disabled son, 56, are believed to have died of carbon monoxide poisoning after the generator malfunctioned.

Meanwhile, a woman, aged in her 50s, died in Madrid after a fire broke out during the blackout. It is believed to have been caused by a candle in the city's Carabanchel district.

A woman aged in her 40s also reportedly died in Valencia. Local reports suggest the woman, who suffered from a lung condition, died after the ventilator she was using lost power.

The emergency services have also confirmed that thirteen people were treated for smoke inhalation. Five of these were taken to hospital for treatment.

The blackout in Spain and Portugal affected around 60 million people. Millions were left without phone and internet coverage, thousands of train passengers were stranded, and people were unable to access cash from ATMS across the Iberian Peninsula.

Flights were also cancelled, with passengers stranded at airports overnight. It was the biggest power cut in Europe since 56 million people lost electricity in Italy and Switzerland in 2003.

Spanish Prime Minister Pedro Sanchez promised to hold power grid operators to account following the blackout. Pedro Sánchez said: "What happened yesterday cannot ever happen again."

Dan Jørgensen, the European Energy Commissioner, added: "The energy situation in Spain and Portugal is back to normal. This incident is the most severe for almost two decades in Europe.

"We stand ready to support Spain and Portugal in all possible ways. Including initiate a thorough investigation."