Large parts of England and Wales were hit by a power outage, leaving almost a million people without electricity as traffic lights were knocked out, trains came to a standstill and aircraft were grounded during rush hour on Friday evening as people prepared to head home for the weekend.

The National Grid Electricity System Operator later said there had been "issues" with two power generators which caused blackouts across London and the southeast, midlands, southwest, northeast and northwest.

Train services in and out of London, including Thameslink, Southern and Gatwick Express were facing delays and cancellations. National Rail said a large number of train services had also been affected. London's Kings Cross station has been closed to avoid overcrowding.

Transport for London said the Victoria line on the city's underground system had been suspended and warned people to take extra care when using the roads because some traffic lights were not working.

Members of the public posted images on social media, which showed the tube network in the darkness and people having to use their mobile phones as torches to find their way out of underground stations and airports. British Transport Police officers were called in to assist station staff and crowds.

The electrical grid operator in northeast England reported multiple power failures across the region, which affected the airport and metro system of the region's biggest city, Newcastle.

Western Power Distribution which serves the Midlands, South West and Wales said there had been a "major incident" but all affected customers now had power restored.

In Cheshire, northwest England, police tweeted that they were aware of a power outage in the Ellesmere Port area.

(With input from Reuters)