The early morning launch came just hours after Pyongyang sent another flurry of trash-bearing balloons southward, this time forcing a three-hour halt to flights in and out of South Korea's Incheon airport.

The missile took off from an area in or around Pyongyang at about 5:30 am (2030 GMT) and South Korean and US intelligence agencies were conducting a detailed analysis, Seoul's Joint Chiefs of Staff said in a statement.

The JCS official said the test of what appeared to be a hypersonic missile ended in failure after a journey of some 250 kilometres (155 miles).

More smoke than usual appeared to emanate from the missile, raising the possibility of combustion issues, the official said, adding it may have been powered by solid propellants.

Japan also confirmed the launch, with its coast guard saying the missile splashed down in the Sea of Japan, also known as the East Sea.

The test follows North Korea launching hundreds more trash-carrying balloons southward on Monday and Tuesday, the latest in a series of border barrages that have sparked a tit-for-tat propaganda campaign.

- Flights suspended -

Seoul's military said the balloons were carrying "mostly paper waste" that posed no safety risk to the public.

But the latest batch of North Korean balloons disrupted takeoffs and landings at Incheon International Airport, an official told AFP.

Both domestic and international flight arrivals and departures "were suspended ... from 1:46 am (1646 GMT) to 4:43 am," an Incheon International Airport Corporation official said.

"At around 4:08 am, it was confirmed that a trash-carrying balloon had fallen near Gate 248 of T2, and military authorities collected it. The airport is operating as normal since 4:44 am," the official added.

Pyongyang has already sent more than a thousand balloons carrying trash in what it says is retaliation for balloons carrying propaganda criticising leader Kim Jong Un's rule floated north by activists.

In response, Seoul has fully suspended a tension-reducing military deal and restarted some propaganda broadcasts from loudspeakers along the border.

- More drills -

South Korea's Marine Corps resumed live-fire exercises on islands near the western inter-Korean border on Wednesday, marking the first such exercises since a 2018 tension-reducing military deal with the North was suspended earlier this month over the balloon-borne propaganda.

The exercise, described by South Korean authorities as "routine and defensive in nature", involved Seoul's K239 Chunmoo multiple rocket launcher systems, among other assets, they said.

It fired "approximately 290 rounds at simulated enemy targets to verify their capability and readiness to strongly retaliate against any provocations", the Marine Corps said in a statement.

On Tuesday, Yoon visited a US aircraft carrier that arrived in South Korea at the weekend for joint military drills aimed at countering North Korean threats.

The drills, which include Japan, are set to go ahead later this month.

Pyongyang has routinely criticised such exercises as rehearsals for an invasion.

Kim's sister and key government spokeswoman Kim Yo Jong warned this month that Seoul would "undoubtedly witness the new counteraction of the DPRK" if the leaflet drops and loudspeaker broadcasts continued.

An activist in the South confirmed Friday that he had launched more balloons.

Legally, South Korea cannot punish activists sending balloons across the border due to a 2023 court ruling that bans it as an unjustifiable infringement on free speech.

Experts have warned that the balloons inadvertently cause border tensions to escalate quickly.

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