Heavy fog on Friday forced the closure of Turkey’s Bosphorus strait in Istanbul, a vital route for Russian oil and other commodities, to shipping traffic, shipping agency GAC said. Six tankers, all over 200 metres long, were waiting to travel south at the mouth of the narrow Bosphorus waterway, which links the Black Sea with the Mediterranean, GAC said. “Traffic has been halted for three hours now, but we don’t know how long it will last,” said Kubilay Ali, assistant general manager at GAC Turkey. Traffic at the Dardanelles Strait, at the other end of the Sea of Marmara, was not affected. Reduced visibility due to poor weather in the winter frequently requires maritime officials to shut the Bosphorus, disrupting the flow of Russian oil and grain to world markets. Each year about 150 million tonnes of crude and petroleum products pass through the waterway, which bisects Istanbul, a city of 15 million people. (Reporting by Ece Toksabay, editing by Dasha Afanasieva)