Earlier, several military aircraft were tracked over the North Atlantic heading towards the vessel, the Marinera. Footage released by Russian media also appears to show a US vessel close to the ship
BBC Verify is following the tanker's journey - it's around 200km (120 miles) south of Iceland and recently changed course
The ship is accused of breaking US sanctions and shipping Iranian oil - it's historically transported Venezuelan crude oil but reports say it's empty at the moment
Earlier, reports said Russia had deployed a submarine and other vessels to escort the tanker across the Atlantic.
Two images published by Russian state broadcaster RT show a helicopter close to a ship that appears to be Marinera.
Features visible on the vessel in the images, including the position of the window and the white and green colour of the metalwork, are consistent with publicly available and satellite images of Marinera.
We’ve asked two experts if they can identify any key characteristics on the helicopters.
