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.

The three countries' defense chiefs also held an annual meeting in Seoul on Friday, where they recognized the importance of close trilateral cooperation.

It was the first time this year that a U.S. B-52H strategic bomber was deployed to the Korea n Peninsula for a drill, conduct ed to improve deterrence against North Korea ‘s increasing nuclear and missile threats, it said.