SEOUL (Reuters) -North Korea fired at least one ballistic missile towards the sea off its east coast, the South Korean military said on Sunday, a day after a top U.S. envoy departed Seoul.

       Seoul's Joint Chiefs of Staff said North Korea had fired an "unknown" missile, without elaborating.

       In recent weeks, North Korea has test fired a range of missiles, including its largest intercontinental ballistic missile (ICBM).

       U.S. Special Representative Sung Kim met his South Korean and Japanese counterparts, Kim Gunn and Funakoshi Takehiro, in Seoul on Friday to prepare for “all contingencies” amid signs North Korea is preparing to conduct a nuclear test for the first time since 2017.

       (Reporting by Byungwook Kim; Editing by Leslie Adler and Lisa Shumaker)