North Korea says leader Kim Jong Un supervised another test-firing of an unspecified new weapon to extend a streak of weapons demonstrations seen as an attempt to pressure Washington and Seoul over slow nuclear negotiations and their joint military exercises.

Pyongyang's Korean Central News Agency on Saturday said Kim following Friday's launches expressed "great satisfaction" over his military's "mysterious and amazing success rates" in recent testing activity and vowed to build up "invincible military capabilities no one dare provoke."

South Korea's military says two projectiles launched from the North's eastern coast flew about 230 kilometers (143 miles) before landing in waters between the Korean Peninsula and Japan.

Friday's launches were North Korea's sixth round of tests since late July.