North Korea has accused the US of engaging in a "hostile military act" and posing a "grave security threat" to the country by sending a nuclear submarine to a South Korean port.
The USS Alexandria entered the Busan port on Monday for supplies and rest for its crew, South Korea’s defence ministry said, adding that the docking would allow the navies of the two countries to promote combined defence posture.
“We express grave concern over the US dangerous hostile military act that can lead the acute military confrontation in the region around the Korean peninsula to an actual armed force conflict," the North's defence ministry said in a statement carried by the KCNA news agency.
Pyongyang said the emergence of the submarine in the peninsula was a “clear expression of the US invariable hysteria for confrontation” against the East Asian country. The North’s armed forces would "unhesitatingly exercise the legitimate right to punish the provokers", it said without elaborating further.
The USS Alexandria, a fast attack submarine armed with Tomahawk cruise missiles, is part of the US Pacific Fleet.
Temporary deployment of US military assets like aircraft carriers, nuclear submarines and bombers to South Korea is not unusual, but Washington has increased the frequency over the last year in a show of force against North Korea.
Pyongyang often responds furiously to such deployments, describing them as proof of hostile intentions, and sometimes reacts with missile tests.
North Korean leader Kim Jong Un has upped his rhetoric against the US since Donald Trump took office last month for his second presidency.
Mr Trump, on his part, has called Mr Kim a "smart guy" and said he would reach out to the Korean leader again after a summit between the two collapsed in 2019 over talks on sanctions relief.
Pyongyang also criticised joint live-fire drills carried out by South Korean and US militaries at a firing range south of the militarised Korean border last week. The drills involved American strategic B-1B bombers.
Earlier this month, the North said it would not tolerate any “provocation” by the US after secretary of state Marco Rubio called it a “rogue state” in an interview.
