The U.S. Coast Guard said Monday that it tracked a group of Russian naval vessels, including two submarines, as they crossed into U.S. waters off Alaska in an apparent effort to avoid sea ice, a move that is permitted under international rules and customs.

Alaska Beacon reporter James Brooks says it coincides with Russia and China conducting joint military exercises in the Sea of Japan.

Eight Russian military planes and four navy vessels, including two submarines, have come close to Alaska in the past week.