The South Korean military claimed on Wednesday that the DPRK fired a long-range ballistic missile, mere days after the latter threatened to shoot down US spy planes that violate its airspace.

Seoul and Washington have ramped up security cooperation in an alliance against the DPRK and vowed that Pyongyang would face a nuclear response if it resorted to tactical nukes against them, in addition to the "end" of its government. 

South Korea's military claims that it detected the launch of a long-range ballistic missile from Pyongyang around 10:00 am (0100 GMT). The Joint Chiefs of Staff (JCS) said, "The ballistic missile was fired on a lofted trajectory and flew 1,000 km (620 miles) before splashing down in the East Sea," referring to the water also known as the Sea of Japan.

The JCS argues that this move "is a grave provocation that damages the peace and security of the Korean peninsula," claiming that it violates United Nations sanctions on Pyongyang and calling on the DPRK to put an end to it. 

A spokesperson for United Nations Secretary-General Antonio Guterres said the UN was "very concerned" while the US, France, and allies expressed strong condemnation. 

US National Security Council Spokesperson Adam Hodge said in a statement, "This launch is a brazen violation of multiple UN Security Council resolutions and needlessly raises tensions and risks destabilizing the security situation in the region."

Read more: Korean peninsula at the brink of nuclear war due to US actions: DPRK

'Come for serious negotiations' 

This comes after the DPRK accused a US spy plane on Monday of violating its airspace and continued to decry US plans to deploy a nuclear missile submarine near the Korean peninsula.

A spokesperson for the DPRK Ministry of National Defense released a statement that the US had "intensified espionage activities beyond the wartime level," citing "provocative" spy plane flights over a period of eight consecutive days this month.

"There is no guarantee that such shocking accident as downing of the US Air Force strategic reconnaissance plane will not happen in the East Sea of Korea," the spokesperson added.

On her part, Kim Yo Jong confirmed that a US spy aircraft violated the DPRK's eastern airspace twice on Monday, adding that it would not respond directly to US reconnaissance activities outside of the country's exclusive economic zone. She warned that it would take "decisive action" if the demarcation of its maritime military line was crossed.

South Korean President Yoon Suk Yeol was also scheduled to attend the NATO summit in Lithuania this week, in an effort to seek stronger cooperation against the DPRK. 

Leif-Eric Easley, a professor at Ewha University in Seoul, said Kim Yo Jong's statement "is part of a North Korean pattern of inflating external threats to rally domestic support and justify weapons tests."

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"Pyongyang also times its shows of force to disrupt what it perceives as diplomatic coordination against it, in this case, South Korea and Japan's leaders meeting during the NATO summit."

In response, NSC Spokesperson Hodge called on the DPRK "to come to the table for serious negotiations."

"The door has not closed on diplomacy, but Pyongyang must immediately cease its destabilizing actions and instead choose diplomatic engagement," he added, highlighting that the US will "take all necessary measures" to ensure the security of its own and its allies, South Korea and Japan.