A magnitude 6.1 earthquake occurred in Turkey's northwestern province of on Sunday evening, sending shocks that were felt some 200 km away in Istanbul.

Turkey's Disaster and Emergency Management Agency said the earthquake was followed by several aftershocks, including one measuring 4.6, and urged citizens not to enter damaged buildings.

Local media reports that one building collapsed in the town of Sindirgi, the epicentre of the earthquake.

Turkey sits on top of major fault lines and earthquakes are frequent.