North Korea launched two missiles into waters off its east coast in a show of anger hours after the US brought a submarine capable of firing nuclear ballistic missiles to a port in South Korea for the first time in about four decades.

North Korea fired two, short-range ballistic missiles early Wednesday morning from a site near Pyongyang’s international airport at around 3:30 a.m. and 3:46 a.m., Yonhap News Agency reported, citing South Korean military officials. The missiles flew about 550 kilometers (340 miles), according to Yonhap.

The launch escalated tensions on the peninsula after the USS Kentucky, an Ohio-class ballistic missile submarine, arrived in the South Korean port of Busan on Tuesday and North Korea detained a US soldier who intentionally walked across the border from the south side of a joint truce village in the Joint Security Area.

The submarine deployment was timed to coincide with the first meeting of a new US-South Korea body that seeks to deter North Korea from deploying its atomic arsenal.

The Nuclear Consultative Group grew out of a Washington summit in April between President Joe Biden and his South Korean counterpart Yoon Suk Yeol, who has sought to move his country closer to the US, including on defense matters.

The group is intended to provide South Korea with a greater say in how America deploys its nuclear umbrella and provide assurances it would be used to retaliate against a North Korean strike.

No ‘Immediate Threat’

The US Indo-Pacific Command said it was aware of the missile launches by North Korea and was conferring with allies and partners. “While we have assessed that these events do not pose an immediate threat to US personnel or territory, or to our allies, the missile launches highlight the destabilizing impact of the DPRK’s illicit weapons program,” the command said in a statement, referring to North Korea by the abbreviation of its formal name.

North Korea has bristled over the US bringing nuclear assets to the region and demanded a halt to any submarine deployments. It has also denounced the Nuclear Consultative Group as a “nuclear war tool.”

“The US should know that its bolstered extended deterrence system and excessively extended military alliance system, a threatening entity, will only make the DPRK go further away from the negotiating table,” Kim Yo Jong, the powerful sister of the North Korean leader, Kim Jong Un, said in a statement published Monday by state media.

--With assistance from Max Zimmerman.