North Korea vowed to strengthen its nuclear capabilities in response to what it called a “provocation” after a U.S. nuclear-powered submarine docked at a South Korean naval base.

In a statement delivered by the Korean Central News Agency on Tuesday, Pyongyang’s defense ministry strongly condemned the arrival of the USS Alexandria (SSN-757), a Los Angeles-class nuclear-powered attack submarine from the U.S. Pacific Fleet to the base in Busan. 

The ministry called the submarine’s presence on the Korean Peninsula “a clear expression of the U.S. invariable hysteria for confrontation” with North Korea, accusing Washington of “openly ignoring the security concerns of