An apparent rebel attack on a key power line plunged around 80 percent of Pakistan into darkness on Sunday, the latest reminder of the country's crippling energy crisis.

The power failure, one of the worst Pakistan has experienced, caused electricity to be cut in major cities nationwide, including the capital Islamabad, and even affected one of the country's international airports.

It came as a fuel crisis grips the country, forcing Prime Minister Nawaz Sharif to cancel his trip to the World Economic Forum in Davos.

Consumers often fail to pay state-mandated power prices in Pakistan, meaning state utilities lose money and cannot upgrade infrastructure.

The latest power failure began after midnight when a transmission line connected to the national grid was damaged in an explosion, officials said, apparently carried out by a separatist group in restive Baluchistan province.

A senior official at the national grid station in Islamabad said around 80 percent of the country was hit by the power outage, while an AFP reporter in the eastern city of Lahore said the city's international airport also suffered a blackout, though flights were not affected.

"The fault in the system was caused by a main transmission line being blown up in Baluchistan," Minister of State for Water and Power Abid Sher Ali said.

Ali apologized for the outage, and blamed ­rebels in Baluchistan, in the country's southwest.

Baluchistan, Pakistan's largest but least developed and most sparsely populated province, has been wracked for decades by a separatist insurgency that was revived in 2004.