In pictures: Electricity restored in big cities of Pakistan after massive blackout

A general view shows Pakistan's capital Islamabad during a power blackout. A major technical fault in Pakistan's power generation and distribution system caused a massive power outage that plunged the country into darkness overnight, country's energy minister Omar Ayub said.

A general view shows port city of Karachi during a power blackout. Hours after the late Saturday outage, Energy Minister Omar Ayub said on Twitter that power was being restored in phases, starting with Islamabad. He said later Sunday that power had been restored to much of the country.

Pakistan Power Minister Omar Ayub Khan speaks during a media briefing along with Information Minister Shibli Faraz (L) in Islamabad, as the country hit by nationwide power blackout.

People are silhouetted on vehicles headlights on a dark street during widespread power outages in Rawalpindi. The blackout was initially reported on social media by residents of major urban centers, including Karachi, Lahore, Islamabad and Multan.

A barber cuts the hair of a customer as a helper uses a mobile phone torch at his shop in Peshawar, as the country hit by nationwide power blackout.

A general view shows city of Islamabad during the power blackout. Minister Ayub said the cause of the power outage was being investigated and work was being done to fire up Pakistan's main Tarbela power station in the northwest, which would lead to a restoration of power in the rest of the country in phases.

Ayub said in a news conference Sunday that the Guddu power plant in southern Sindh province developed a fault at 11:41 p.m. that triggered the shutdown of other power plants in seconds. | Above: A motorcyclist rides through a residential area during a power blackout in Karachi.

Later, Zafar Yab, spokesman for the Ministry of Energy, said the Tarbela and Warsak plants, both in northwestern Khyber Pakhtunkhwa province, had come back online and power was being restored to the transmission system. | Above: People and auto rickshaws are silhouetted on vehicles headlights on a dark street in Rawalpindi.

Yab said restoration of power to all areas of the country would take some time, however. | Above: A general view shows the city of Islamabad during blackout.

Tailors sit at their shops in Peshawar, as the country hit by nationwide power blackout.

People walk through a residential area during the power blackout in the port city of Karachi.

People are silhouetted on a vehicle headlights on a dark street during widespread power outages in Rawalpindi.

Motorists drive through a residential area during blackout in the port city of Karachi.