The power-cuts affected the central Sabail and Nasimi districts and much of the rest of the city.
There was some confusion over the cause of the blackout. Baku power grid Bakielektrikshebeke referred enquiries to the state-owned power utility Azerenerji.
Azerenerji said the power cut was caused by a failure on the Absheron high-voltage line. Engineers had restored power to the capital, the company said in a statement broadcast on local TV.
According to the Emergencies Ministry hotline, the power cut was caused by an outage at one of the generating units at the Severnaya (North) power station north of Baku. Power from Severnaya reaches the city via the Absheron line.
The unit is back in operation and power is being restored to Baku in phases, the ministry said.
Power was also cut to the Baku underground. Trains came to a halt at noon. Rescue workers and firefighters from the Emergencies Ministry were dispatched to the city's underground stations. Over two and a half hours later, at 14.42 local time, the operation to evacuate passengers from the carriages was coming to an end.
Many trapped passengers telephoned local news agencies to tell them of their plight. They reported some panic amongst passengers. Many passengers needed first aid treatment but no-one had to be taken to hospital.
Some parts of the city remain without power. There was another blackout in the Badamdar area for 35 minutes at 14.55 local time.
According to Azerenergy, the emergency meeting attended by leaders of Azerenergy and other responsible institutions, the problems such as the disconnections in the energy system, causes and the ways of solution are being discussed. The meeting is still continuing and Azerenergy is expected to give and official announcement to public regarding to the problem.
Due to the problem Bakielektrikshebeke is also hosting a deliberation.
Power cuts in north
Repairs to the high voltage power line from Mingacevir hydro-electric power station to the north-west of Azerbaijan cut power to Sheki, Zagatala, Balakani and Gakh districts at 12.10 local time.
The town of Gusar and surrounding villages in the north-east of Azerbaijan were also left without power today.
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