There were no reports of deaths or major damage in the tremor with an epicentre in the Düzce province, about 200 km east of Istanbul.
ADVERTISEMENTA magnitude 5.9 earthquake hit a town in northwest Turkey early on Wednesday, causing damage to some buildings and injuring at least 68 people.
The earthquake was centred in the town of Gölyaka in Düzce province, some 200 kilometres east of Istanbul, the Disaster and Emergency Management Presidency said.
It struck at 4:08 am (2:08 CET) and was felt in Istanbul, the capital Ankara and other parts of the region. Dozens of aftershocks were reported, including one magnitude of 4.3.
The quake woke people from their sleep, and many rushed out of buildings in panic in the province that has experienced earthquakes in the past.
At least 68 people were treated in hospitals for injuries, mostly sustained during the panic to flee their homes, jumping from balconies or windows.
One of them was in serious condition, Interior Minister Süleyman Soylu told private NTV television.
"We almost completed our checks in the villages around Gölyaka. There is no severe damage reported; only some barns were wrecked in these places," Soylu said on the state-run broadcaster TRT Haber.
"There was a power cut during the quake but authorities are reinstating power now," he said.
Power was cut in the region as a safety measure, the minister said.
The quake demolished the exterior cladding and parts of the roof of a courthouse in Düzce, HaberTurk television reported. Among other damage, a two-story shop collapsed on a narrow street, it said.
In Gölyaka, people gathered in the main square, some wrapped in blankets distributed by the emergency management agency.
Düzce Governor Cevdet Atay said schools in the region were being closed as a precaution.
Around 800 people were killed in a powerful earthquake that hit Düzce on 12 November 1999.
In August of that year, 17,000 people were killed by another powerful quake that devastated nearby Kocaeli province and other parts of northwest Turkey.
Officials said around 80% of the buildings in the area were rebuilt or fortified following the 1999 earthquakes, which helped minimise damage.
Turkey sits on top of major fault lines and is frequently shaken by earthquakes.