The launch comes after UN sanctions monitoring against the nuclear-armed nation was upended last month by Pyongyang's ally Russia.

South Korea's military said it had detected the launch of "several short-range ballistic missiles" from the Pyongyang area, which flew around 300 kilometres (186 miles) before splashing down into waters east of the Korean peninsula.

"This missile launch is a blatant provocation that threatens peace and stability of the Korean peninsula," South Korea's Joint Chiefs of Staff said, adding that the military was maintaining "full readiness".

Tokyo also confirmed the launch, with Japanese government spokesman Yoshimasa Hayashi saying one missile had a maximum altitude of 50 kilometres and landed outside of the country's EEZ.

The launch is the second in less than a week by Pyongyang, which on Friday tested a "super-large warhead" designed for a strategic cruise missile, state media said. Seoul's military confirmed it had detected cruise missile launches at the time.

Pyongyang's ally Moscow in March used its United Nations Security Council veto to effectively end UN monitoring of violations of the raft of sanctions on Kim Jong Un's government for its nuclear and weapons programme.

Analysts have warned that North Korea could be testing cruise missiles ahead of sending them to Russia for use in Ukraine, with Washington and Seoul claiming Kim has shipped weapons to Moscow, despite UN sanctions banning any such moves.

Seoul claims Pyongyang has sent around 7,000 containers of weapons to Moscow for use in Ukraine.

Pyongyang's recent track record on launches indicates the North is trying to push its technical abilities, said Hong Min, a senior analyst at the Korea Institute for National Unification.

"Today's launch also appears to be a part of its weapons development programme that needs testing rather than ones that are fully developed," he told AFP.

Unlike their ballistic counterparts, the testing of cruise missiles is not banned under current UN sanctions on North Korea.

- Russia ties -

The largely isolated country has recently bolstered military ties with Moscow, and this month it thanked Russia for its veto blocking the renewal of a panel of UN experts that monitored international sanctions against it.

It has also ramped up testing, claiming in early April to have tested a new medium-to-long-range solid-fuel hypersonic missile.

"Despite Russia's veto of renewing the mandate of the UN panel of experts, Security Council sanctions on North Korea remain in place," Leif-Eric Easley, a professor at Ewha University in Seoul said.

"The problem is that Seoul and Washington are increasingly focused on domestic politics while Russia and China prioritise political rivalries."

This year, Pyongyang has declared South Korea its "principal enemy", jettisoned agencies dedicated to reunification and outreach, and threatened war over "even 0.001 mm" of territorial infringement.

Last year, the North conducted a record number of missile tests in defiance of UN sanctions in place since 2006 and despite warnings from Washington and Seoul.

Pyongyang declared itself an "irreversible" nuclear weapons state in 2022.

US Secretary of State Antony Blinken, who was in Seoul last month, will be back in the region this week making his second visit in less than a year to China.