A string of drone attacks on at least seven cargo vessels in the Black Sea this month, off the coasts of NATO members Romania and Bulgaria, has some members of the alliance wondering if Russian President Vladimir Putin is seeking escalation to test their support for Ukraine in its war against Moscow's full-scale invasion.
The attacks in the two countries' exclusive economic zones threaten a global shipping route and have left two people dead, with at least 25 still missing. They also run the risk of drawing other countries directly into the war for Ukraine.
