Top South Korean, U.S. and Japanese military officers are urging North Korea to cease all unlawful activities that threaten regional security, as the three nations fly 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.

A North Korean man crossed the DMZ on foot before midnight Thursday, asking South Korean troops for help in a rare defection through the fortified border.

The fishermen’s boats had drifted into South Korean waters, officials said. The South’s new president has been trying to improve ties with North Korea.

South Korea on Wednesday repatriated six North Koreans across the maritime border in the East Sea, months after they drifted into southern waters and were rescued.

The Wonsan Kalma resort was opened in a grand ceremony last month by North Korea's leader, Kim Jong Un, who hailed it as a "world-class tourist and cultural destination". The details of how this resort was built have been shrouded in secrecy in a country largely closed to the outside world.

South Korea returned on Wednesday six North Koreans who had become stranded at sea earlier this year after their vessels had drifted south, Seoul's Unification Ministry said on Wednesday.

SEOUL (Reuters) -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 two U.S. allies over international waters, Yonhap news reported, citing the South's defence ministry.

South Korea's chairman of of the joint chiefs of staff hosted his counterparts from the U.S. and Japan in Seoul on Friday.