A Canadian naval vessel recently completed an operation to monitor North Korea’s illicit maritime activities near Japan, as the U.S. and its allies look for new ways to track sanctions violations in lieu of U.N. investigations.

According to a statement released by Japan’s Ministry of Foreign Affairs on Wednesday, the Royal Canadian Navy frigate HMCS Ottawa focused on activities “including ship-to-ship transfers involving North Korean-flagged vessels that are prohibited under United Nations Security Council resolutions.”