People watch a television screen showing a news broadcast with file footage of a North Korean missile test at a railway station in Seoul on October 28
People watch a television screen showing a news broadcast with file footage of a North Korean missile test at a railway station in Seoul on October 28 AFP

North Korea fired one intercontinental ballistic missile and two short-range missiles Thursday, although the longer-range launch appeared to have failed, Seoul's military said.

People on a South Korean island and in parts of northern Japan were ordered to seek shelter during Thursday's launches by the North, which followed a blitz of missiles fired on Wednesday.

The largest of those launches, however, appeared to have failed.

"North Korea's ICBM launch is presumed to have ended in failure," the South Korean military said.

Seoul's military said earlier it had detected the launch of the long-range ballistic missile at around 7:40 am (2240 GMT) in the Sunan area of Pyongyang.

Shortly after, it detected what were "believed to be two short-range ballistic missiles fired at around 08:39 am from Kaechon, South Pyongan province."

South Korea's military "is maintaining a full readiness posture while closely cooperating with the US and strengthening surveillance and vigilance," it said.

Pyongyang fired more than 20 missiles on Wednesday, including one that landed near South Korea's territorial waters.

The multiple missile launches come as Seoul and Washington are staging their largest-ever joint air drills, involving hundreds of warplanes from both sides.

Pyongyang has called the US-South Korean air exercise, dubbed Vigilant Storm, "an aggressive and provocative military drill targeting the DPRK," and warned that, if it continues, Seoul and Washington will "pay the most horrible price in history."

Local media reported that air raid sirens had gone off on South Korea's eastern island of Ulleungdo -- where residents were warned on Wednesday to seek shelter after one of Pyongyang's short-range ballistic missiles crossed the de facto maritime border.

Tokyo also confirmed Thursday's launches, with the Japanese government issuing a special warning to residents of northern regions, telling them to stay indoors or seek shelter.

Tokyo initially said the missile had flown over Japan, prompting a "J-Alert" to be issued, but defence minister Yasukazu Hamada later said "the missile did not cross the Japanese archipelago, but disappeared over the Sea of Japan."

Given the missile was "accompanied by evacuation warnings, strongly suggest IRBM or possible ICBM on full-distance launch," Chad O'Carroll of Seoul-based specialist site NK News said on Twitter.

"Latter could be very worrying for some if it successfully goes a significant distance."

Washington and Seoul have repeatedly warned that Kim's recent missile launches could culminate in another nuclear test -- which would be Pyongyang's seventh.

The blitz of launches indicates "Quite possible tactical nuclear weapons test(s) will be next. Possibly very soon," O'Carroll added.

Ahn Chan-il, a North Korean studies scholar, agreed.

"These are North Korea's pre-celebration events ahead of their upcoming nuclear test," he told AFP.

"They also seem like a series of practical tests for their tactical nuclear deployment."

North Korea revised its laws in September allowing for pre-emptive nuclear strikes, with leader Kim declaring the country to be an "irreversible" nuclear power -- effectively ending negotiations over its banned arms programs.

On October 4, North Korea fired a missile over Japan that also prompted evacuation warnings. Pyongyang later claimed it was a "new-type ground-to-ground intermediate-range ballistic missile".

It was first time North Korea had fired a missile over Japan since 2017.

Pyongyang later claimed that the launch and a blizzard of other tests around the same time were "tactical nuclear drills" that simulated showering South Korea with nuclear-tipped missiles.

One short-range ballistic missile crossed the Northern Limit Line, the de facto maritime border, on Wednesday, prompting President Yoon Suk-yeol to call it "effectively a territorial invasion".

Pyongyang also fired an artillery barrage into a maritime "buffer zone" on Wednesday.

South Korea, for its part, said it fired three air-to-ground missiles into the sea close to the two countries' maritime boundary.

Seoul also closed some air routes over the East Sea, advising local airlines to detour to "ensure passenger safety in the routes to the United States and Japan".