The North Korean military has revealed details of missile operations it conducted from Wednesday through Saturday.

The ruling Workers' Party newspaper, Rodong Sinmun, on Monday quoted the General Staff of the Korean People's Army as saying it conducted the military operations in response to joint air drills being carried out by the United States and South Korea.

The General Staff said its forces fired four tactical ballistic missiles on Wednesday to simulate a strike on an enemy air force base.

It also said its forces fired two strategic cruise missiles at the open sea around 80 kilometers off the coast of Ulsan City, South Korea, later that day.

South Korea's military said one of the missiles crossed the de facto inter-Korean maritime border for the first time.

The North's General Staff also noted its military units conducted test-firings of ballistic missiles on Thursday to "verify the movement reliability" of a warhead. It said its forces fired "super-large multiple launch missiles and tactical ballistic missiles."

The South Korean military reported that a missile that the North launched on that day may have been a Hwasong-17, a new type of intercontinental ballistic missile.

The North Korean military stressed it will continue to respond to all enemy war drills with "overwhelming practical military measures."