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. Earlier today, disruption had been reported at Lahore's international airport, and two nuclear power plants remain offline. 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. A spokesman added: "The blowing up of two power pylons in Naseerabad last night created a backward surge which affected the system. It was an act of sabotage." 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. Many people struggle to meet the low costs for electricity, leaving utility companies without the cash needed to upgrade infrastructure.