In a statement carried by the KCNA news agency, Ri Pyong Chol, vice-chairman of the Central Military Commission of the ruling Workers’ Party, denounced joint military exercises by the US and South Korea as openly showing their “reckless ambition for aggression.”

South Korean and US forces began live-fire exercises simulating a “full-scale attack” from North Korea last week in what they said were the biggest such drills to demonstrate their “overwhelming” military capability against the North’s threats.

North Korea’s Ri said the drills required Pyongyang to have the “means capable of gathering information about the military acts of the enemy in real time.”

The statement did not specify the exact launch date, but North Korea has notified Japan of the planned launch between May 31 and June 11, prompting Tokyo to put its ballistic missile defences on alert.

Nuclear-armed North Korea says it has completed its first military spy satellite and leader Kim Jong-un has approved final preparations for the launch.

Japan has vowed to shoot down any projectile that threatens its territory, saying any North Korean missile launch would be a serious violation of UN Security Council resolutions.