North Korean ruler Kim Jong Un said a new naval destroyer was damaged in a "serious accident and criminal act caused by absolute carelessness."

Kim has framed the arms buildup as a response to perceived threats from the United States and its allies in Asia, who have been expanding joint military exercises amid rising tensions over the North’s nuclear program. He says the acquisition of a nuclear-powered submarine would be his next big step in strengthening his navy.

North Korea has opened an investigation into a failed warship launch earlier this week after leader Kim Jong Un said the accident threatened the country's dignity, state media reported. On May 21, Kim was in attendance at a launch ceremony for a new naval destroyer when a "serious accident" occurred,