ISTANBUL 

A magnitude 4.2 earthquake shook Istanbul on Thursday, said Turkey's disaster agency.

Disaster and Emergency Management Authority (AFAD) said the quake hit the Sea of Marmara at 4.38 p.m. local time (1338GMT) and it was off the coastal district of Marmaraereglisi in the northwestern Tekirdag province, neighboring Istanbul, a city of more than 15.5 million.

Its epicenter was 6.83 kilometers (4.23 miles) beneath the surface.

Governor’s office in Istanbul said no casualties have been reported so far.

“There has been no negative developments reported due to the earthquake,” said the office.

In 1999, a magnitude 7.4 tremor hit the industrial province of Kocaeli to Istanbul's east, leaving over 18,000 people dead.

*Writing by Sena Guler