North Korea "fires unidentified ballistic missile toward East Sea", Seoul's Joint Chiefs of Staff said, referring to the body of water also known as the Sea of Japan.

Japanese broadcaster NHK, citing government sources, said the missile "appeared to be short range and has already fallen".

The launch came hours after Kim Yo Jong accused Seoul and Washington of "misleading the public opinion" on the issue with their repeated accusations that Pyongyang is sending weapons to Moscow for use in Ukraine.

She said the North's "tactical weapons including multiple rocket launchers and missiles shown by us recently are produced to discharge the only one mission... to prevent Seoul from inventing any idle thinking."

The launch is the latest since the North fired a volley of what Seoul said were short-range ballistic missiles off its east coast on April 22.

North Korea is barred by rafts of UN sanctions from any tests using ballistic technology, but its key ally Russia used its UN Security Council veto in March to effectively end UN monitoring of violations, for which Pyongyang has specifically thanked Moscow.

The UN panel of experts was investigating allegations that North Korea was transferring weapons to Moscow, with Seoul claiming in March that some 7,000 containers of arms had been sent to Russia for use in Ukraine since around July 2023.

Washington and experts have said Pyongyang is seeking a range of military assistance from Russia in return, such as satellite technology and upgrading its Soviet-era military equipment.

The North said last week it would equip its military with a new 240mm multiple rocket launcher this year, adding that a "significant change" for the army's artillery combat capabilities was underway.

- Reaction to drills? -

Kim Jong Un inspected a new tactical missile weapons system on Tuesday and called for an "epochal change" in war preparations by achieving arsenal production targets.

Analysts say the nuclear-armed North could be ramping up production and testing of artillery and cruise missiles before sending them to Russia for use in Ukraine.

The launch also comes a day after advanced South Korean and US stealth fighters, including Washington's F-22 Raptors, staged joint air combat drills.

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

The North has appeared especially sensitive to air drills in the past, with experts noting its air force is the weakest link in its military.

"It appears that this is a counter-military demonstration in response to recent South Korea-US air exercises," Yang Moo-jin, president of the University of North Korean Studies in Seoul, told AFP.

"It also appears to contain a warning message regarding the large-scale South Korea-US joint exercises scheduled for August," Yang said.

Inter-Korean relations are at one of their lowest points in years, with Pyongyang declaring South Korea its "principal enemy".

It has jettisoned agencies dedicated to reunification and threatened war over "even 0.001 mm" of territorial infringement.