Russia Steps Up Strikes on Ukraine Grain Ports as U.S. Warns of Ship Attacks

Russia on Thursday stepped up its aerial assaults on Ukrainian ports critical to the world’s food supply, as the White House warned that the Kremlin has mined sea routes and might be setting the stage for attacks on commercial transport ships.

Moscow has already put shipping companies on notice that they now cross the Russian blockade in the Black Sea at their own peril, and could be treated as military targets. The warning came days after Russia pulled out of a multinational deal that had…