North Korea has been urged to "stop the provocative acts" after firing missiles from its east coast early on Sunday morning.
The missiles were launched from the city of Sinpo at around 6.10am (10.10pm on Saturday UK time) and flew around 90 miles into the Sea of Japan, South Korea's military said.
The launch is North Korea's fourth this month and the seventh of the year - and comes amid a ramping up of the demonstrations since the beginning of the Iran war.
Experts have said Pyongyang's missile activity is meant to display its self-defensive capabilities in an effort to gain international leverage.
"The missile launches may be a way of showing that - unlike Iran - we have self-defence capabilities," said South Korean former presidential security adviser Kim Ki-jung.
"The North also appears to be exerting pressure pre-emptively and make a show of force before engaging in dialogue with the United States and South Korea," he added.
It is unclear what kind of ballistic missiles were fired on Sunday, however Sinpo is home to several submarines and equipment for test-firing submarine-launched ballistic missiles.
The North last fired a ballistic missile from a submarine in May 2022 and it flew as far as 370 miles.
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Officials have warned that the Iran war may reinforce Pyongyang's nuclear ambitions.
North Korea has made "very serious" advances in its ability to turn out nuclear weapons, with the probable addition of a new uranium enrichment facility, International Atomic Energy Agency chief Rafael Grossi warned on Wednesday.
Late last month, Mr Kim said Pyongyang's status as a nuclear-armed state was irreversible and expanding a "self-defensive nuclear deterrent" was essential to national security.
US President Donald Trump has repeatedly expressed interest in holding talks with the North Korean leader when he visits Asia next month.
(c) Sky News 2026: North Korea launches missiles into the sea in latest show of force
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