Top South Korean, U.S. and Japanese military officers urged North Korea to cease all unlawful activities that threaten regional security, as the three nations flew advanced warplanes for a joint exercise in a show of force against the North.

South Korea, Japan and the United States conducted a joint air drill on Friday involving a U.S. B-52 strategic bomber and fighter jets of the three allies over international waters, the South's defence ministry said.

The U.S. Air Force has transferred upgraded F-16 Fighting Falcons from Japan to South Korea, reinforcing its fighter capabilities on the Korean Peninsula amid ongoing efforts to deter airborne threats.