An earthquake with a preliminary magnitude of 6.2 has jolted Istanbul and nearby areas on Wednesday, Turkey's disaster and emergency management agency said.
There were no immediate reports of serious damage in the metropolis of 16 million.
More than 150 people were hospitalised with injuries sustained while attempting to flee buildings, the Istanbul governor's office said.
The earthquake had a shallow depth of 10 kilometres, according to the United States Geological Survey, with the epicentre about 40 kilometres southwest of Istanbul in the Sea of Marmara.
It was felt in the neighbouring provinces of Tekirdağ, Yalova, Bursa and Balıkesir and in the city of Izmir, some 550 kilometres south of Istanbul.
There were several aftershocks, including one measuring magnitude 5.3.
The incident, which started at 12:49 pm local time during a public holiday when many children were out of school and celebrating in the streets, caused widespread panic in Istanbul, which is on tenterhooks due to the looming threat of a major earthquake.
Panicked residents rushed from their homes and buildings into the streets. The disaster and emergency management agency urged people to stay away from buildings.
"Due to panic, 151 of our citizens were injured from jumping from heights," the Istanbul governor's office said in a statement.
"Their treatments are ongoing in hospitals and they are not in life-threatening condition."
Many residents flocked to parks, school yards and other open areas to avoid being near buildings in case of collapse or subsequent earthquakes. Some people pitched tents in parks.
"Thank God, there does not seem to be any problems for now," President Recep Tayyip Erdoğan said at an event marking the National Sovereignty and Children’s Day holiday.
"May God protect our country and our people from all kinds of calamities, disasters, accidents and troubles."
Leyla Ucar, a personal trainer, said she was exercising with her student on the 20th floor of a building when they felt intense shaking.
"It threw us around, we couldn't understand what was happening, we didn’t think of an earthquake at first because of the shock of the event," she said. "It was very scary."
Turkey's interior minister, Ali Yerlikaya, said authorities had not received reports of any collapsed buildings but told HaberTurk television that there had been some reports of damage.
Turkey is crossed by two major fault lines, and earthquakes are frequent.
A magnitude 7.8 earthquake on 6 February 2023 and a second powerful tremor that came hours later, destroyed or damaged hundreds of thousands of buildings in 11 southern and southeastern provinces, leaving more than 53,000 people dead.
Another 6,000 people were killed in the northern parts of neighbouring Syria.
While Istanbul was not impacted by that earthquake, the devastation heightened fears of a similar quake with experts citing the city’s proximity to fault lines.
In a bid to prevent damage from any future quake, both the national government and local administrations started urban reconstruction projects to fortify buildings at risk and started campaigns of demolishing buildings at risk of collapse.
