Armed Islamists fighting the Pakistani government caused a widespread blackout affecting at least 140 million people on Sunday by attacking an electric transmission facility.
80 percent of the country's population were without power following the assault on the station in southwestern Baluchistan.
It was one of the worst blackouts to ever hit the Islamic Republic of Pakistan and affected the international airport in Lahore.
The minister of energy promised via Twitter that his office would work tirelessly to end the outage. Power returned to about half of the country throughout Sunday, but many remained in darkness.
Pakistan, which has fought Islamist rebels such as the Taliban for years, has already been dealing with a severe energy crisis, which caused Prime Minister Nawaz Sharif to cancel his trip to the World Economic Forum in Davos.
Blackouts have become common in Pakistan as shortages of natural gas and oil are felt, but large-scale outages such as this are very unusual.
Pakistan's military has been carrying out a wide offensive against Islamists in North Waziristan, and claims to have killed more than 2,000 terrorists. The army has lost 200 soldiers. The government announced on Sunday that bombing by the military had killed 35 gunmen in the northwest, near the Afghanistan border.