ISTANBUL, Jan. 7 (Xinhua) -- Heavy snowfall in northwestern Turkey have caused flight delays and cancellations in Istanbul on Monday.

In a warning issued on its website, Turkish Airlines, the national flag carrier, called on its passengers to regularly check their flight details before arriving at airports, citing "expected adverse weather conditions in Istanbul."

Among the halted flights of Turkish Airlines from Istanbul were also some international ones to Bulgaria's capital Sofia, Serbia's capital Belgrade, Greece's Thessaloniki, Moldova's capital Chisinau, Croatia's Dubrovnik and Ukraine's Odessa.

The heavy snow across the Thrace region is also disturbing daily lives, forcing the schools to close and disrupting highway transportation.