Turkish Airlines has cancelled its five Friday flights to the Iranian capital Tehran, which has been rocked by protests against the rising cost of living, according to the Istanbul Airport app.
Five other flights operated by Iranian airlines have also been cancelled, according to the airport app, while seven others remain scheduled.
Turkish authorities have not commented so far on the situation in Iran, where protesters have challenged the authorities under Ayatollah Ali Khamenei.
The Iranian government was already battling an economic crisis after years of sanctions and recovering from the June war against Israel.
Rights groups have accused Iranian security forces of opening fire on demonstrators, with the Norway-based NGO Iran Human Rights saying Thursday that security forces had killed at least 45 protesters, including eight minors, since the demonstrations began
According to the specialist website Flight Radar, a Turkish Airlines plane flying to Shiraz and a Pegasus flight to Mashad turned back from Iranian airspace on Thursday night.
Turkey shares a border of around 500 kilometres (300 miles) with Iran, and there are three active land crossings between the two countries.
