North Korea fired at least one ballistic missile, South Korea'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 to 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.
Mr Trump has said he hopes to meet North Korean leader Kim Jong Un, possibly this year, following several meetings during his first term.
North Korea has said Mr 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" intercontinental ballistic missile at a military parade attended by top officials from Russia and China.
It added that the strike range of the new Hwasong-20 "knows no bounds".
Mr Kim oversaw in September a test of a solid-fuel engine used for long range nuclear missiles.
State media said it was the ninth and final test of the engine, indicating that a full test-fire of the new ICBM could be conducted in coming months.
North Korea has for years staged test flights of long-range missiles apparently able to reach the continental United States.
It has also rolled out solid-fuel variants that are easier to mobilise, conceal and launch rapidly compared with liquid-fuel missiles.
The United States demand that Mr Kim give up his banned weapons has long been a sticking point between the two countries, with North Korea under successive rafts of UN sanctions over its nuclear and missile programmes.
North Korea has repeatedly stated this year that it has no intention of giving them up.
But North Korea has also recently indicated a fresh openness to talks with the United States.
Mr Kim met Mr Trump three times for high-profile summits during the US leader's first term, before talks collapsed in Hanoi in 2019 over what concessions North Korea was prepared to make on its atomic weapons.
Mr Kim in September said he had "fond memories" of Mr Trump and was open to another meeting.
"If the United States discards its delusional obsession with denuclearisation and, based on recognising reality, truly wishes for peaceful coexistence with us, then there is no reason we cannot meet it," state media quoted him as saying.
