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.

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.

South Korea's Unification Ministry said Friday the two Koreas should resolve any inter-Korean issues through dialogue, as North Korea continues to dismantle a reunion facility for separated families inside its Mount Kumgang tourist area.

North Korea is developing chemical weapons to use on the battlefield in preparation for full-scale war, according to a high-level official within the regime.