This assumption is based on the data by the vessel positions tracking system marinetraffic.com. Other countries' vessels did not show this strange manner of moving, Censor.NET reports referring to the Center for Transport Strategies.
Later in the evening, the vessels finally entered Bosporus.
Here are some screenshots showing the movement of Russia's vessels at the entrance to Bosporus. Bratsk general cargo vessel (second screen shot) was moving in circles from 10 a.m. to 7 p.m., while Volgobalt's zigzagging started at 3 a.m. to last until 4 p.m.