A massive power cut has hit dozens of provinces in Turkey, causing transport chaos across the country.
More than half of Turkey's 81 provinces were hit, with officials saying a break in connections with mainland Europe could be to blame.
The cut hit at 10:36 (07:36 GMT) on Tuesday morning, and power was not fully restored until the evening.
Prime Minister Ahmet Davutoglu has said all possible causes are being examined, including terrorism.
Traffic lights stopped working in several parts of Istanbul and Ankara during the outage, causing traffic jams, while rescue teams were called to help people trapped in lifts or stuck underground at metro stations.
By Tuesday afternoon, electricity returned to parts of Istanbul. At 20:40 (17:40 GMT) Energy Minister Taner Yildiz said that power had been restored across the country, Hurriyet reported.
Mr Yildiz said officials would investigate what had caused the outage.
"It is too early to say now if it is because of a technical reason, a manipulation, a foul play, an operational mistake, or a cyber [attack]. We are looking into it... We cannot say they are excluded possibilities."
Turkey suffers from sporadic electricity cuts but locals say they cannot remember such a nationwide cut for a generation, reports the BBC's Mark Lowen in Istanbul.
One of the few cities unaffected by the power cut was Van in the east of the country, where electricity is supplied from Iran.