The Democratic People's Republic of Korea (DPRK) fired an unidentified projectile into eastern waters, South Korea's Joint Chiefs of Staff (JCS) said on Monday without mentioning further details.
It marked the DPRK's fourth projectile launch this year.
The DPRK's Korean Central News Agency said last week that the railway-borne missile regiment test-fired two tactical guided missiles on Friday.
The DPRK said it successfully test-launched a hypersonic missile on Jan. 5 and Jan. 11 respectively.