A Russian cargo plane sanctioned by the U.S. over its alleged role in supporting the invasion of Ukraine detoured to North Korea this week, an unusual flight that experts say raises concerns about U.N. sanctions violations and potential DPRK-Russia arms transfers.

The Il-76TD freighter (tail number RA-76842) departed Shanghai’s Pudong International Airport at around 5:30 p.m. KST on Monday and flew north across the Yellow Sea before making a sudden turn toward Pyongyang around 1.5 hours into the flight, the aviation tracker Flightradar24 shows.