The South Korean Joint Chiefs of Staff (JCS) said it detected the launch from the Tongchang-ri area on North Korea’s west coast at 11:05 a.m. (02:05 GMT) on Sunday.
"While strengthening its monitoring and vigilance in preparation against the possibility of additional launches, our military is maintaining a full readiness posture in close cooperation with the United States," the JCS said in a statement, quoted by Yonhap.
The latest test-firing comes three days after Pyongyang launched a Hwansong-17 intercontinental ballistic missile in response to joint military drills held by the United States and South Korea over 11 days called "Freedom Shield 23." Pyongyang condemned the drills, calling them preparations for a "war of aggression."
North Korea also claimed on Friday that 800,000 of its citizens volunteered to fight against the United States "Imperialists and puppet traitors [who] are trying to destroy our independence and right to live and develop."
The Japanese Coast Guard also stated that the object fired by North Korea could be a ballistic missile, and has issued a warning following the launch.
According to Japanese media, the missile landed outside of Japan's exclusive economic zone. The missile test also comes days after leaders of South Korea and Japan agreed on stronger security cooperation.