Pakistan was plunged into darkness after a key power transmission line broke down early on Sunday in an incident being initially blamed on a rebel attack, 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 throughout the country, including the capital Islamabad.

This was the fourth major breakdown of the system within the past one month plunging countless cities, towns and villages in Punjab, Khyber Pakhtunkhwa and Balochistan into darkness. A substantial area in Sindh was affected, too.

QESCO officials said that power supply to Quetta and other parts of Balochistan was suspended as a result of technical fault from Guddu transmission line.

However, the spokesman of the Baloch Republican Army, Sarbaz Baloch, claimed that the defunct militant group had carried out the bombing of two 220 kv transmission lines in Notal area of Balochistan's Nasirabad district.

Prime Minister Nawaz Sharif took notice of the power breakdown and issued instructions for the immediate resumption of power supply on an emergency basis. Power supply in many areas was restored after instructions were issued by the prime minister.

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

The tripping of Guddu power plant's transmission lines affected the 500KV power line from the national grid, forcing Jamshoro and Bin Qasim power stations to shut down.

Dawn's Quetta correspondent, Syed Ali Shah, earlier reported that in Balochistan 17 districts suffered a sudden power breakdown. According to Quetta Electric Supply Company (QESCO) officials, the transmission lines from Guddu to Quetta were tripped.

Power supply to Quetta and other 16 districts have been suspended as a result of technical fault, however, it could not be verified by independent sources.

QESCO officials said, supply of electricity through 220KV transmission line was abruptly suspended. The other districts include Pishin, Khuzdar, Mastung, Kalat, Sibi, Bolan and other adjoining areas.

Federal State Minister for Water and Power Abid Sher Ali said that transmission lines in Balochistan's Nasirabad district were blown up by a bomb which caused the electricity crises.

DawnNews reported that more that 70 per cent of Karachi had plunged into darkness. A K-Electric spokesperson told Dawn that the power supply had been partially restored in Karachi and the supply to remaining areas would resume soon.

Earlier today, Dawn's correspondent in Islamabad, Sohail Iqbal Bhatti, had reported that the country's power crisis would be exacerbated as a result of acute shortage of furnace oil. The shortage of furnace oil had also been revealed by the Water and Power ministry in a report on handling of furnace oil shortage issues.

The report said that power production from Jamshoro power plant has been decreased to 170MW from 570MW.

Similarly, power generation from Muzaffargarh plant after a decrease of 700MW was 360MW only, while Faisalabad power plant has suspended power generation due to non-availability of furnace oil.

Also, power production from HUBCO and Kapco after a decrease of 1300MW stood at 1051MW. Due to acute shortage of furnace oil, power shortfall has stood above 6700MW in the country.

According to the power ministry’s report, demand of electricity has surged to 14000MW, while the generation has reduced to only 7,000MW.

Refineries are unable to fulfill the demands of furnace oil, while a decision to purchase 12 cargoes of furnace oil has been facing a shortfall of Rs30 billion.

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.

In addition to chronic infrastructure problems, the energy sector is also trapped into a vicious “circular debt” brought on by the dual effect of the government setting low electricity prices and customers failing to pay for it.State utilities therefore lose money, and cannot pay private power generating companies, which in turn cannot pay the oil and gas suppliers, who cut off the supply.

Earlier this week, Prime Minister Nawaz Sharif cancelled his trip to the World Economic Forum in Davos to deal with a severe petrol shortage at home.

The fuel crisis began last week when Pakistan State Oil was forced to slash imports because banks refused to extend any more credit to the government-owned company, which supplies 80 percent of the country's oil.

Solving Pakistan's energy crisis was a key campaign pledge for Sharif in the run-up to the 2013 general election, and the shortage is heaping fresh pressure on his government.