ISTANBUL: A snowstorm that sharply reduced visibility in Turkey's Bosphorus Strait forced maritime authorities to shut the key shipping channel on Tuesday, shipping agent GAC said.

Traffic for all northbound and southbound vessels was suspended at 11:45 a.m. (0945 GMT) because of the poor visibility, GAC said in an email. It was the second day of intermittent closures.

The snowstorm also prompted flag carrier Turkish Airlines to cancel 76 flights scheduled for Tuesday and Wednesday, after cancelling dozens of flights on Monday due to the weather, according to its website.

GAC said the Dardanelles Strait at the other end of the Sea of Marmara remained open to tanker traffic.

The Bosphorus and Dardanelles are the only maritime outlet for oil, grain and other commodities from Russia and other Black Sea countries. Poor weather frequently forces their closure in winter.

Each year, some 10,000 vessels carrying 150 million tonnes of oil and petroleum products pass through the straits.