North Korean media report that the country test-fired two strategic cruise missiles from a submarine early on Sunday morning.
Showing some photos, the Korean Workers Party's newspaper Rodong Sinmun reported on Monday the underwater launching drill.
South Korea's Joint Chiefs of Staff says it detected the North Korean missile launch from a submarine in waters near the North's eastern city of Sinpho on Sunday morning.
North Korea says it launched four strategic cruise missiles on February 23. The country's missile launches from a submarine were also the first since May of last year.
The move came just before the United States and South Korea begin a joint military exercise on Monday.