Two U.S. B-52 heavy bombers made a rare training flight with the Air Self-Defense Force over the Sea of Japan last week, in a mission that likely comes in response to a spate of North Korean short-range missile tests over the last several months.

The bombers, which flew from Andersen Air Force Base on the U.S. territory of Guam, conducted training with ASDF "off the coast of Japan" on Friday, U.S. Pacific Air Forces (PACAF) spokeswoman Capt. Victoria Hight said.

While she did not reveal if the mission had occurred over the Sea of Japan, aviation tracker Aircraft Spots tweeted an image of the planes' flight path showing them into the waterway. It said three KC-135R aerial tankers also provided support for their flight.