Hundreds of millions of Pakistanis were left without power due to a technical fault in the country's power distribution system, government officials said on Sunday. The government has launched an investigation to find out the cause of the blackout.

The blackout began at about 11.50 p.m. on Saturday when power failures were reported in all major cities, including Islamabad, Lahore, Peshawar, Karachi and Rawalpindi, reports Xinhua news agency.

According to the National Transmission and Despatch Company, the system had tripped, and it may take a while to restore power. The country began restoring power to cities one by one starting with Islamabad. However, large parts of major cities still remain under blackout.

The blackout was caused after the frequency in the national power distribution system suddenly fell from 50 to zero, Federal Minister for Energy Omar Ayub Khan said in a tweet, adding that "we are trying to ascertain what caused the drop in frequency".

He said that attempts are being made to fire up the Tarbela power station which will lead to a sequential restoration of power supply.

<em>(With inputs from IANS)</em>.