The downpour began in Istanbul's northern districts of Arnavutkoy and Basaksehir, as well as in the area of Istanbul New Airport around 9 p.m. local time on Tuesday (18:00 GMT). As of 10 p.m. local time, the downpour has not yet reached the southern parts of the city, the correspondent reported.
The Istanbul authorities warned in advance of the downpour in a number of northern districts and urged residents not to leave their homes without necessity.
Local media reported the downpour flooded the Basaksehir subway station in northern Istanbul. Several roads were also flooded, causing traffic jams.
Turkish media indicated a number of people were trapped in a library in Basaksehir, and were waiting for the arrival of rescuers.
At least two people died after being caught in the flood caused by the rain in the Basaksehir and Kucukcekmece municipalities of Istanbul Province, media reported, citing the province's authorities. An investigation into the deaths have since been undertaken.
At least four people were missing as a result of the floods in the city of Kırklareli in the European part of Turkiye, media reported, adding that the country's defense ministry sent a military group to help.
Istanbul Mayor Ekrem Imamoglu confirmed a number of streets in several districts in the west of the city were flooded, adding that authorities did not expect such a downpour. Some 150 kilograms (330 pounds) of precipitation per square meter fell in some areas, he said. Over 2,100 people were working to deal with the consequences of the natural disaster.
Istanbul authorities have suspended water supply for irrigating gardens and private parks in the city since early September against the background of droughts.