A massive power outage has knocked out electricity across parts of Spain and Portugal, shutting off traffic lights and causing chaos at airports, train stations and on the roads.

Spanish power grid operator Red Electrica said it was working with energy companies to restore power.

“The causes are being analysed and all resources are being dedicated to solving it,” it said.

“We will continue to inform you.”

Portugal’s police force said traffic lights and street lighting were at risk of failing.

“Reduce your speed and pay extra attention,” they said, instructing people to avoid unnecessary journeys.

“Prioritise safe driving: your calmness saves lives,” its statement added.

Spanish train operator Renfe said there was a power outage at a national level, causing trains to stop and departures to be canceled.

E-Redes, which provides electricity to mainland Portugal, said in a statement it was working to re-establish connection.

“This is a wider European problem,” the company said in a statement, according to Reuters.

Spain and Portugal have a combined population of more than 50 million people. It is not immediately clear how many people are affected.

At lunchtime in the Alcântara neighbourhood in Lisbon, the streets were busy with cars and pedestrians but the shops were dark.

Many were still operating using pen, paper and cash to record purchases but there were longer than usual lines as shoppers chatted uneasily while they waited.

It wasn’t exactly panic buying but cans of beans and tuna were in high demand.

One young couple realised that without cash, and with ATMs not working, they didn’t have any way to pay for anything.

Traffic seemed to still be flowing normally and the occasional plane flew overhead on a warm April day.

Barber Hugo Fernandes, 42, was still cutting hair this afternoon but said he probably only had three or four cuts left before the shaver batteries ran out.

“I think a little bit we were already expecting all these sorts of things,” he said.

“We, at times, I think, let things happen and while they don’t happen, I think people think they will never happen.”