A North Korean tanker sanctioned by the UN and U.S. was photographed by Japanese air and naval forces conducting suspected ship-to-ship oil transfers on consecutive days earlier this month, the Japanese foreign ministry reported Friday.

It is the second report from Japan’s Ministry of Foreign Affairs (MOFA) since November, and follows another report in June which also dealt with ship-to-ship (STS) transfers involving a single DPRK tanker connecting to smaller vessels over the course of multiple days.