Lahore: Key Pakistani cities have been left without power, triggered by  a "frequency variation" in the national grid, on Monday, media reports said.

Power failure has been reported in different cities including Karachi, Lahore, Islamabad, Peshawar and Quetta.

Power Minister Khurrum Dastagir, while talking to Geo News, said that the power generation units are temporarily shut down in winter at night as an economic measure to save fuel costs.

“When the systems were turned on at 7:30am this morning one by one, frequency variation was reported in the southern part of the country between Jamshoro and Dadu. There was a fluctuation in voltage and power generating units were shut down one by one due to cascading impact. This is not a major crisis,” said the federal minister as the country plunged into darkness for the second time in four months.

 The minister said that his ministry has started restoring some grid stations in Tarbela and Warsak.

"Peshawar Electric Supply Company (PESCO) and some grids of Islamabad Electric Supply Company (IESCO) have already been restored," claimed the minister.  

"We provide K-Electric about 1,000-1,100 megawatts routinely, however, it will be restored within a few hours. It is not certain how long will it take to sort this issue. However, my target is to restore electricity in the country in the next 12 hours," said the minister.