A massive blackout has struck Pakistan overnight, leaving many without electricity as officials rush to restore power.

The outages began early Sunday morning. Authorities gave no estimate for how many people the blackout affected, though electricity went out in nearly every major city in this country of 180 million people.

A spokesman for the Ministry of Water and Power, Zafaryab Khan, said a militant attack on a transmission tower in the southwestern Baluchistan province cause the blackout. Khan said that caused a power surge that eventually affected wide swaths of the power distribution system.

By morning, power had been partially restored to many parts of the country.

Pakistan often suffers through long hours of electricity outages, as well as periodic natural gas and gasoline shortages.