The power failure, one of the worst Pakistan has experienced, caused electricity to be cut in major cities throughout the country, including the capital Islamabad.

It was later restored in much of the country, with the national power company saying normal distribution would resume within hours.

Officials said the blackout began after midnight when a transmission line connecting a privately-run power plant to the national grid was damaged.

A senior official at the National Grid station in Islamabad said around 80 percent of the country was hit by power breakdown.

An AFP reporter in the eastern city of Lahore said the airport was also affected by the breakdown. 

Minister of State for Water and Power Abid Sher Ali later issued an apology and said electricity had been restored in most of the country, blaming the breakdown on rebels blowing up the line in Naseerabad district, which lies in southwestern Baluchistan province.

A spokesman for the national power company said that "electricity has been restored in all parts of the country."

"Some 6,000 megawatts of electricity has been added to the national system and within a couple of hours distribution will be normal," the spokesman said.

Pakistan's electricity distribution system is a complex -- and delicate -- web and a major fault at one section often leads to chain reactions and breakdowns of power generation and transmission.