Istanbul, Jan 25 : Istanbul Airport, the largest of the three airports in Istanbul, has cancelled all flights for safety concerns, after the Turkish metropolis and financial hub was swept by a strong snowstorm, according to the airport management. "All flights at Istanbul Airport have been temporarily halted for flight safety due to bad weather conditions," the airport management announced in a Monday post on Twitter. Istanbul Governor Ali Yerlikaya asked locals not to travel unless necessary, and warned that heavy snowfall is forecast in the city center during the evening rush hour, Xinhua news agency reported. Public employees were allowed to end their shifts at 3:30 p.m. local time (1230 GMT), according to Yerlikaya. The Istanbul Governor's Office said in a separate statement that due to the snowstorm, vehicles heading from the Thrace area in the northern part of the country to Istanbul would not be allowed to enter the city. More than 7,400 municipal teams in Istanbul had been working around the clock to keep the roads open, according to Ekrem Imamoglu, Mayor of the city with a population of nearly 16 million. Heavy snowfall stranded 4,603 persons on roadways around the country in the last 24 hours, according to the Disaster and Emergency Management Authority. Turkish authorities issued a five-day extreme weather alert on Friday, warning of heavy and continuous snowfall, ice, and strong winds in most parts of the country. /IANS