North Korea fired at least one ballistic missile on Wednesday, Seoul's military said, its first such launch in months.
It comes a week before a meeting of APEC leaders, including US President Donald Trump, is due take place in the South Korean city of Gyeongju.
South Korea's Joint Chiefs of Staff said the "unidentified" missile flew east.
The launch is the nuclear-armed North's first of its kind since South Korean President Lee Jae-myung took office in June.
Trump has said he hopes to meet North Korean leader Kim Jong Un, possibly this year, following several meetings during his first term.
Pyongyang has said Kim is open to future talks, with caveats that it will not agree to relinquish its nuclear arsenal.
North Korea showed off this month what it called its "most powerful" intercon