A Russian military plane made an unannounced trip to Pyongyang this week, days after defense minister Sergei Shoigu’s high-profile visit and talks with leader Kim Jong Un, according to NK News analysis of flight tracking data and satellite imagery.

Details such as the purpose of the visit from Tuesday to Wednesday and personnel involved are still unknown, with Russian and North Korean state media yet to report on the matter. But it appears related to following up on Shoigu’s delegation visit and possibly agreements made with Kim.