Russian naval activity in the Black Sea likely seeks to deter shipping to Ukrainian ports without formally blockading them, the Institute for the Study of War said in its daily report. 

The institute notes recent instances of Russian forces warning civilian vessels away from Ukrainian ports.

A Russian warship told a ship that sailing to Ukraine could get it treated as a military target, according to an intercept shared by Ukrainian officials.

Meanwhile, Russia imposed restrictions near the Kerch Strait over alleged Ukrainian drone concerns, the think tank added. It said naval drills, where Russian naval warships launched a missile at a target ship in the Black Sea on 27 July and earlier Russian statements threatening merchant ships have exacerbated uncertainty.

The institute assesses that the ambiguous Russian naval posturing appears aimed at chilling maritime traffic to Ukraine without committing resources to enforce an actual blockade. A blockade requires declaration, which Russia has not done.

Maritime security in the Black Sea is an international problem