What impact is the blackout in Spain and Portugal having and how long will it last?

An "exceptional and extraordinary" power outage has brought large parts of Portugal and Spain to a standstill.  Public transport services, internet connectivity and ATM machines across the Iberian Peninsula, an area home to 50 million people, have been affected by the outage, which occurred suddenly just after midday local time (11.30am UK time).

Blackouts latest: Follow live updates Work is ongoing to try and restore power to affected parts of the two nations - including the capitals of Madrid and Lisbon - with Portugal's grid operator warning it could take up to a week for the network to fully normalise again. Here is everything you need to know.

What has been affected and where? Huge swathes of Spain and Portugal, including major cities like Barcelona, Lisbon, Madrid, Porto and Seville have been affected by the power outage. Parts of the Basque region in France were also briefly affected.

As traffic lights stopped working, traffic began to pile up on roads. In Barcelona, civilians worked to direct traffic at junctions along the Gran Via avenue, a road that cuts through the city.

Spain's traffic authority, DGT, then urged citizens to not use their cars unless absolutely necessary. A similar situation occurred on the railways.

Train services in both countries ground to a halt, with Spanish television showing people evacuating from metro stations in Madrid and empty stations with trains stopped in Barcelona. Maddie Sephton, who is from west London, was on the Madrid Metro when the power outage occurred.

She told Sky News "everything went dark" on the train and she had to exit the station by hiking up 15 flights of stairs with her luggage. "No lifts are operating - making it difficult for elderly people with limited mobility," she added.

Above ground, she said that "everyone is just standing around and waiting". Passengers at airports in Lisbon, Madrid and Barcelona are also facing disruption.

Spanish airports were operating on backup electrical systems and some flights were delayed, according to Aena, the company that runs 56 airports in Spain. While in Lisbon, terminals closed and crowds of tourists sat outside in the sun and the shade waiting for news about their flights.

The power outage occurred as three matches were ongoing at the Madrid Open. The Spanish parliament in Madrid has since closed play and suspended the tournament.

US tennis star Coco Gauff was in the middle of a post-match interview when the power cut happened. The 2023 US Open champion later posted on an Instagram showing only emergency lighting working in a locker room.

Other things that have been affected include:• Internet and mobile coverage;• Lighting in homes, businesses and other buildings, though backup generators are in place in many;• ATMs and card payment machines, as well as most till systems;• Lifts in buildings• Electric car chargers and fuel pumps;• Air conditioning units;• Several Spanish oil refineries;• A large quantity of water pumps, meaning some homes have no access to drinking water. What caused the outage? No official cause of the blackout is yet to be determined, but Portugal's grid operator REN has said it was down to a fault in the Spanish electricity grid, related to a "rare atmospheric phenomenon".

REN said due to extreme temperature variations in Spain, there were "anomalous oscillations" in very high-voltage lines. The operator said this is known as "induced atmospheric variation.