Seoul - South Korean President Moon Jae-In called for the "strongest punishment" against North Korea, including new United Nations sanctions, after Pyongyang said it successfully tested a hydrogen bomb Sunday. Moon called for "all diplomatic measures including UNSC sanctions resolutions to completely isolate North Korea", presidential security adviser Chung Eui-Yong said after an emergency National Security Council meeting. The South would discuss deploying "the strongest strategic assets of the U.S. military", he cited Moon as saying -- potentially a reference to tactical nuclear weapons which were withdrawn by Washington in 1991.