ISTANBUL, Dec 11 (Reuters) - Turkey's maritime authority said on Sunday that four tankers, carrying some 475,000 tonnes of oil, had provided the necessary insurance letters according to regulations and would cross the Istanbul Strait on Dec. 12. A Turkish measure in force since the start of the month has caused shipping delays. It requires vessels to provide proof of insurance covering the duration of their transit through the Bosphorus Strait or when calling at Turkish ports. In a statement, the authority also said it removed five oil tankers from the country's territorial waters via the Dardenelles Strait as they could not provide confirmation letters for their insurance. Reporting by Ezgi Erkoyun; Editing by Alex RichardsonOur Standards: The Thomson Reuters Trust Principles.

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