A massive power breakdown in Pakistan on Monday affected most of the country's more than 220 million people, including in the mega cities of Karachi and Lahore.
Local outages are common across Pakistan, and the national power system is a complex and delicate web where problems can quickly cascade.
The hours-long outage, the second in two years, was caused by a fault in the national grid at around 7.30am (0230 GMT).
"According to initial reports, the system frequency dropped at the national grid in the morning which led to a massive breakdown," the ministry of energy tweeted.
Repair work was underway, with limited power restored in parts of the capital and the northwestern city of Peshawar.
The port city of Karachi, with a population of more than 15 million, and Lahore, with a population of more than 10 million, remained without power.
"We hardly managed to come to school as there was no electricity at home," said 25-year-old Karachi teacher Vareesha Nadeem.
"Here in classes we are using battery-powered lights but they'll run out soon. Power outages have just become a part of our lives as they happen so often."
A shop owner in the megacity told AFP he feared his entire dairy stock would spoil without refrigeration, and 39-year-old printer Khurrum Khan said orders were piling up because of the blackout.
Unreliable power is "a permanent curse which our governments have failed to overcome," Khan complained.
In the garrison city of Rawalpindi, neighbouring Islamabad, most shops were struggling without power.
Homeware trader Muhammad Iftikhar Sheikh, 71, said he was unable to demonstrate electronic products to browsing customers.
"The customers never buy without testing first," he said. "All of us are sitting idle."
A similar breakdown in January 2021 plunged the entire country into darkness after a fault occurred in southern Pakistan, tripping the national transmission system.
Pakistan has long been hit by energy shortages because of a combination of factors including a poor economy, mismanagement and a lack of storage facilities.
Hospitals are mostly backed up with generators and schools use gas to heat their classrooms.
Load shedding this winter has impacted domestic households and industries including textile manufacturing, one of the largest industries in Pakistan, with some plants temporarily closed.