The South Korean military announced Saturday morning that Pyongyang had fired an unspecified missile.
The United States and members of the UN Security Council have imposed several rounds of sanctions on North Korea since North Korea's first nuclear test in 2006.
Despite the sanctions, North Korea has insisted on strengthening its military capability to counter the threat of US troops in the region.
North Korea says it will not back down from its missile and nuclear program until the United States ends its hostile policy to overthrow the Pyongyang regime.