The European Commission says it is "in contact" with Spanish and Portuguese authorities "to understand the underlying cause" of today's blackout.

"The commission will keep monitoring the situation and make sure that there is smooth information exchange," a spokesperson for the EU's executive arm says.

European Commission President Ursula von der Leyen has also been in touch with Spain's Prime Minister Pedro Sánchez. European authorities will "coordinate efforts and share information to help restore the electricity system", von der Leyen writes on social media.

Antonio Costa, a former Portuguese premier who heads the European Council of EU member states, is also in contact with the Spanish and Portuguese leaders, EU officials add.

Image source, Getty Images

Some final remarks from Portugal's power firm REN, which goes on on to say that, "due to the complexity of the phenomenon and the need to rebalance electricity flows internationally, it is estimated that full normalisation of the network could take up to a week".

Earlier, the head of Spain's electricity network said that restoring power could take between six and 10 hours.

We have a bit more for you now from the Portuguese energy company REN (Rede Eletrica Nacional).

It says that "due to extreme temperature variations in the interior or Spain, there were anomalous oscillations in the very high voltage lines (400 KV), a phenomenon known as 'induced atmospheric vibration'".

"These oscillations caused synchronisation failures between the electrical systems, leading to successive disturbances across the interconnected European network."

As we said in our last post, Spain is yet to respond to these claims.

We're now hearing from Portugal's grid operator, REN, which says interruptions to the country's power supply were the result of a "fault in the Spanish electricity grid.

They say this was related to a "rare atmospheric phenomenon", but don't clarify what that means.

Spain is yet to respond to the claim.

We'll bring you more on this in our next few posts.

Holly Wallis
Live reporter

Will David, 40, a Briton living in Lisbon, says he was having a haircut and beard trim in the basement of a barbers in Lisbon when the power went down.

"Customers needing electric razors had to leave in various states of haircut and shave completion," says Will.

Rita, the barber, kindly found him a spot by the window upstairs to finish the cut with scissors and left Will looking "halfway presentable".

"The walk home felt very strange, both with the lack of traffic lights meaning a complete free-for-all for vehicles and pedestrians on the roads - as well as so many people milling around outside their places of work with nothing to do."

Image source, Getty Images

Josh Parry
LGBT and identity reporter

Curtis Gladden, 29, is originally from Liverpool but recently moved to in La Vall D’Uixo, about 30 miles from Valencia.

He tells BBC News his phone signal hadn’t worked for around two hours, which he says was "scary" as he struggled to get updates about what was happening.

Now the signal has returned, he and other locals are using the time without electricity to get outside and enjoy a drink in the town’s pavement cafes.

It’s a local holiday in some parts of Spain, known as Saint Vincent Ferrer’s day.

Curtis and his partner Miguel were hoping to join in the festivities but say they are "uncertain" whether they’ll take place.

He says: "Nothing is working; we came to get some food and a drink but they can’t cook without electricity. There’s supposed to be a festival today but we’re not sure if it will happen now."

Molly Stazicker
Transport reporter

Image source, Reuters

In our last post, we brought you an update from some of the affected airports across Spain and Portugal.

Now Gatwick, in London, has also reported issues - telling the BBC it's experiencing short delays on flights to Spain and Portugal.

The airport says there have so far been no cancellations and it's waiting for the issues to be resolved.

Meanwhile, airline Ryanair says it's monitoring potential disruptions to flights operating to and from all airports in mainland Spain and Portugal.

Let's have a quick look now at the situation at airports.

Madrid's international airport - Adolfo Suárez Madrid-Barajas - and Barcelona's Josep Tarradellas Barcelona-El Pratairport currently have notices saying "some incidents are occurring" as a result of the outage. The airports add that contingency generators are active, but warn anyone travelling to check with airlines as disruptions may affect access and ground transportation.

Lisbon and Porto airports similarly warn that "operation constraints" may occur.

Portuguese news agency Lusa is reporting that airport operator Ana has activated emergency generators - enabling essential operations to continue in Porto and Faro, but Lisbon is seeing further limitations.

Looking at departure boards, airports including Madrid, Barcelona and Porto are seeing delays.

Bernadette McCague
BBC News

Emily Thorowgood, who's from Bristol but who works as a teacher in an international school in Lisbon, has told the BBC she is currently "teaching in the dark" after the power went off at around noon local time.

"Lots of parents are taking their children out due to the power cuts," she says.

"It was flashing on and off for a long while but seems to have finally given up."

Image source, Getty Images

Bernadette McCague
BBC News

Image source, EPA

Lesley has lived in Spain for 11 years with her husband. The couple are currently based in Murcia, Spain.

"There's very little news about what's happened," she tells the BBC.

"We are worried about food, water, cash and petrol in case this goes on for a couple of days."

She says there's "more to worry about" than the Madrid Open tennis tournament being suspended.

"My husband is driving around now trying to find a petrol station that's open to get petrol for the generator so that we can plug in the fridge."

Image source, EPA

Pedro Sánchez is currently hosting an "extraordinary" meeting of Spain's national security council, the prime minister's press office says in a statement on social media, external.

We're yet to hear an update from the meeting, but when we do we'll let you know.

James Kelly
BBC News

In the Spanish resort of Benidorm, Mark England tells us how the lack of power has disrupted his holiday.

He says he and his partner Jonnie had gone for lunch when the lights in the dining room started to go off.

"Then everything went off and the fire alarm started going off and the fire doors started closing," he tells the BBC.

"There’s still no power. We’re walking down the main street now and the majority of shops are in darkness and shuttered up or have people on the entrances saying you can’t come in.

"There’s no cash machines, no traffic lights so it’s strange. It’s kind of bizarre."

Worst of all, at a holiday destination like Benidorm, Mark says bars are unable to serve drinks because of a lack of power to their pumps.

"If you haven’t got a drink, you are out of luck," he says.

The head of Spain’s electricity grid says restoring power could take hours.

Speaking at a news conference, Red Electrica CEO Eduardo Prieto tells reporters that the operation to solve the issue could take "between six and ten hours".

We'll bring you more on this as soon as we get it.

It's been more than two hours since a massive power cut left swathes of Spain and Portugal without power.

What we know so far

• In some regions, trains have been evacuated, traffics lights are out, and shops and restaurants have been plunged into darkness
• The internet is also affected and mobile phone networks are reportedly down in Spain
• Spanish grid operator Red Electrica says it's working with regional energy companies to restore supplies
• In Madrid - the capital of Spain - Mayor José Luis Martínez-Almeida has warned residents to stay where they are
• Meanwhile, in Portugal, airline TAP Air tells passengers not to travel to airports until further notice
• Parts of France also briefly lost power but the French grid operator RTE says the network is now operating normally

What we don't yet know

• How and why this happened - local authorities say they're racing to figure this out
• When power will be fully restored, with Spanish Prime Minister Pedro Sánchez's office saying: "The government is working to identify the origin of this incident and dedicating all possible resources to resolve it as quickly as possible"

Image source, Reuters

Image source, Getty Images

We've now heard from the mayor of Madrid, who's asking residents to stay put where possible.

"I ask all residents of Madrid to keep their movements to an absolute minimum and, if at all possible, to remain where they are. We want to keep all roads clear," José Luis Martínez-Almeida says in a video posted on social media.

Speaking from the integrated emergency security centre of Madrid he says that on top of traffic lights being off, tunnels of certain highways have had to be closed.

The mayor also asks residents to only call emergency services if it is "truly urgent": "If emergency calls go unanswered, go to the police and the fire stations in person, where they will try to deal with all the emergencies which may present themselves."

Joaquin Sorolla train station in Valencia, Spain, is full of passengers who are stranded after their trains were affected by the power outage.

Earlier, Spain's national railway company Renfe said the "entire National Electricity Grid" had been "cut off".

Image source, Reuters

Image source, Reuters

Image source, Reuters

Hannah Lowney, who is from Manchester but lives in Madrid, says she was halfway through scanning her grocery shopping in Aldi when the power went out.

In a voice message to the BBC's Naga Munchetty, on Radio 5 Live, she explains:

"Looking out the window it seemed like it was the whole street [that lost power], and then the people in Aldi said it was a nationwide power cut.

"The traffic lights are out. People are coming out of their offices and walking home because they can’t tell when the buses are coming.

"It seems no one has an idea of when it will come back.

"It’s a bit disconcerting that it’s the whole country, I’ve never experienced this before."

Image source, Reuters

Image source, Reuters

Mobile phone networks have also been hit by the massive power cut.

Reporters for the AFP news agency in Madrid and Barcelona saw people heading into the streets, holding their smartphones up to try to connect to a network.

Many people used the radio, rather than their phones, to get updates, the news agency says.

Portuguese airline TAP Air has warned passengers not to head to airports until further notice.

In a statement on its Facebook page, the airline says some services are not operating as usual and asks passengers to await more information.

Parts of France temporarily lost power following the outages in Spain and Portugal, Reuters news agency reports, citing French grid operator RTE.

A spokeswoman for RTE gives no further detail on the extent of the outage, but says that power has now resumed after the brief interruption.