North Korea fired several cruise missiles towards the sea off the west coast of the Korean peninsula in the early hours of Saturday, according to the South Korean military.
Details of the launch are being analyzed by South Korean and US intelligence authorities, South Korea's Joint Chiefs of Staff said in a statement.
On Thursday state media KCNA reported that Pyongyang had conducted a simulated "scorched-earth" nuclear strike on targets across South Korea.
Seoul announced sanctions on Friday on five North Korean individuals and one company in response to Pyongyang's launch of what it said was a space rocket last month.