Millions of homes have been plunged into darkness following one of the worst blackouts in Pakistan's history.

More than 140 million people - up to 80% of the population - lost electricity after militants attacked a transmission tower and caused a massive power surge.

Only around half of those affected have so far had their power restored.

Pakistan's energy minister tweeted: "On the Prime Minister's directive, we are not to sleep until this problem is resolved."

It could be hours before the grid returns to normal, as a major fault in one part of the network causes disruption nationwide.

Pakistan is currently facing an energy crisis, with Prime Minister Nawaz Sharif cancelling his trip to the World Economic Forum in Davos to deal with a petrol shortage earlier this week.