The United States, South Korea and Japan staged joint naval missile defence drills off the Korean peninsula on Tuesday, as North Korea accused Washington and its allies of creating “the most unstable waters with the danger of a nuclear war.”

The three nations staged exercises in international waters off South Korea’s southern Jeju island to improve their ability to detect and track targets, and share information in the event of provocation by Pyongyang, South Korea’s military said.

The drills come as North Korean leader Kim Jong Un has called for “radically” modernising the weapons and equipment of its naval forces, criticising an increased presence of US strategic assets in the region.

In a speech to mark Navy Day, Kim said the “gang bosses” of the United States, Japan and South Korea announced regular joint military exercises, news agency KCNA reported, apparently referring to their Aug. 18 summit at Camp David, Maryland.

“Owing to the reckless confrontational moves of the US and other hostile forces, the waters off the Korean Peninsula have been reduced into the world’s biggest war hardware concentration spot, the most unstable waters with the danger of a nuclear war,” Kim was quoted by KCNA as saying.

In the first standalone meeting between the leaders of the US, South Korea and Japan, the three agreed to deepen military and economic cooperation as they seek to project unity in the face of China’s growing power and the North’s nuclear threats.

South Korea and the United States last week began the Ulchi Freedom Shield summer exercises, designed to enhance their joint responses to North Korea’s nuclear and missile threats. Pyongyang has long denounced the drills as a rehearsal for war.

“The prevailing situation requires our navy to put all its efforts into rounding off the war readiness to maintain the constant combat alertness,” Kim said, adding the naval forces would become part of the “state nuclear deterrence carrying out the strategic duty”.