There will be no war on the Korean peninsula, South Korean President Moon Jae-In said Thursday, despite high tensions over the North's nuclear and missile programmes.

"All South Koreans have worked so hard together to rebuild the country from the ruins of the Korean War," Moon told a press conference marking his first 100 days in office.

"I will prevent war at all cost," he added. "So I want all South Koreans to believe with confidence that there will be no war."