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.

It comes a week before a meeting of APEC leaders, including US President Donald Trump, in the South Korean city of Gyeongju.

Trump has said he hopes to meet North Korean leader Kim Jong Un again, possibly this year.

Pyongyang has said Kim is open to future talks -- with caveats that it will not agree to relinquish its nuclear arsenal.

This month, North Korea showed off what it called its "most powerful" intercontinental ballistic missile at a military parade attended by top officials from Russia and China.