The move comes amid growing North Korea-Russia ties after Russian President Vladimir Putin and North Korean leader Kim Jong-un signed a "comprehensive strategic partnership" treaty that would allow North Korea to take action if either side is armed. There has been a call to provide military assistance to each other without any delay. Yonhap news agency reported that the attack.

North Korea's Foreign Ministry said, "The US and its followers' steps to strengthen the military bloc will never be ignored... but will be taken to protect the state's sovereignty, security and interests and the region through aggressive and coercive countermeasures." "Peace will be vigorously defended." said a statement carried by the country's official Korean Central News Agency.

The ministry did not elaborate on what it meant by retaliatory measures.

On Saturday, South Korea, the US and Japan concluded their first, three-day trilateral multi-domain military drills, codenamed "Freedom's Edge", aimed at strengthening their deterrence against North Korean threats.

The three countries have conducted joint maritime and air exercises before, but Freedom's Edge was the first trilateral exercise conducted across multiple domains, including air, maritime, underwater and cyber.