A letter provided by Russian insurer, Ingosstrakh, enabled the first oil tanker to sail through Turkish waters in recent days after tougher regulations were imposed by Turkish authorities, a document showed, Reuters reports.
This has led already at least 20 oil tankers backed up in the Turkish Straits as they do not have the right paperwork.
Turkish authorities introduced new requirements, which came into effect on 1 December, in which every ship must have insurance cover in place for all circumstances when sailing through Turkish waters or when calling at ports.
Ingosstrakh provided the requirements for the Liberia flagged "Vladimir Tikhonov" tanker, which included insurance for pollution risks throughout the period in Turkish waters, according to a letter issued to the authorities on 29 November by the insurer and seen by Reuters.
The world's leading Western ship insurers say they are unable to provide cover for all circumstances, arguing they cannot be liable for payouts if, for instance, there are sanctions breaches with a ship's cargo.
"Vladimir Tikhonov" completed sailing through the Bosphorus on 3 December, ship tracking data showed.