"North Korea fired an unidentified ballistic missile east," South Korea's Joint Chiefs of Staff said in a statement, without giving further details.

Japan's coast guard also confirmed the launch of a suspected North Korean ballistic missile, warning vessels to be vigilant.

Nuclear-armed North Korea has carried out a record-breaking blitz of weapons tests this year, including firing short-range ballistic missiles four times last week.

Pyongyang's bout of intense weapons testing comes as Seoul, Tokyo and Washington ramp up joint military drills to counter growing threats from the North.

South Korea, Japan and the US staged anti-submarine drills Friday -- the first in five years -- just days after Washington and Seoul's navies conducted large-scale exercises in waters off the peninsula.

Such drills infuriate North Korea, which sees them as rehearsals for an invasion.

US Vice President Kamala Harris was in Seoul last week and toured the heavily fortified Demilitarized Zone that divides the peninsula, on a trip that aimed to underscore her country's "ironclad" commitment to South Korea's defence against the North.

South Korean and US officials have also been warning for months that North Korean leader Kim Jong Un is preparing to conduct another nuclear test.

US and South Korean officials have said they believe this could happen soon after China's upcoming party congress on October 16.

North Korea, which is under multiple UN sanctions for its weapons programmes, typically seeks to maximise the geopolitical impact of its tests with careful timing.