Ukraine has struck a Russian shadow-fleet tanker in the Black Sea off Sochi, according to reports. The Liberian-flagged Aframax tanker Rio, already sanctioned by Ukraine, was reportedly hit by naval drones and caught fire. Thick black smoke was seen from the resort city, and tourists were told to stay indoors as smog filled the air. Russia has not commented on the blast. The attack came in view of Sochi’s holiday crowds and the area near President Vladimir Putin’s official residence. On the same day, Russia struck a Marshall Islands-flagged merchant ship in the Black Sea, killing at least one crew member. Two more ships were hit about 70 miles off Bulgaria’s coast inside its exclusive economic zone. One sank within minutes and the other caught fire. Two crew members were severely injured and several are missing. The strikes mark a sharp and dangerous escalation in the Black Sea shipping war.