A major power outage hit cities and provinces across Turkey on Tuesday, including the capital of Ankara and the biggest city, Istanbul, where parts of the subway and tram system shut down and shopping malls plunged into darkness.
Prime Minister Ahmet Davutoglu said all possible causes of the outage were being investigated and did not rule out sabotage, but said that trouble with transmission lines was the most likely reason for the problem.
People carrying jerry cans queued at petrol stations to buy fuel for generators as the power cut dragged on for more than four hours. Road junctions were clogged as traffic lights went out.
"Our main target right now is to restore the network. This is not an incident that we see frequently,'' Energy Minister Taner Yildiz said during a trip to Bratislava, in comments broadcast on Turkish television.
"Whether or not terrorism is a high possibility or a low one I can't say at this stage. I can't say either whether it is a cyber attack,'' he said in response to questions from reporters.
Yildiz later said around 80 percent of Istanbul's power supply had been restored and that the rest of the country would follow soon.
Turkey's sole oil refiner, Tupras, said its production was not affected. Airports operator TAV said operations were normal at major airports, including Istanbul, Ankara and Izmir.
Broadcaster NTV said power cuts were reported in more than 40 of Turkey's 81 provinces. The power transmission company TEIAS could not immediately be reached.
Yildiz said power was cut to many regions at 10:36 am (0736 GMT), apparently due to a problem with transmission lines. He said a government crisis center had been set up.
Turkey's electricity consumption has risen strongly in recent years, thanks to robust economic growth and a rising population. It has been forced to ramp up energy investments and imports of natural gas, its biggest source for power generation.
Such widespread power outages are rare. Energy officials quoted by the newspaper Hurriyet said it was Turkey's biggest blackout in 15 years.