Pyongyang, North Korea - North Korea's military has vowed to take "sustained, resolute and overwhelming" measures in response to the joint US-South Korean military air exercises.

The Korean People's Army (KPA) general staff alleged the joint drills were "in fact, an open provocation aimed at intentionally escalating the tension in the region and a dangerous war drill of very high aggressive nature directly targeting" North Korea.

"The serious situation prevailing on the Korean peninsula due to the reckless military hysteria of the U.S. and south Korea is now moving toward the more unstable confrontation," an English-language statement carried by state news agency KCNA on Monday read.

The North Korean military conducted its own drills to simulate attacks on air bases and aircraft and "smash the enemies' persistent war hysteria," the KPA said.

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It confirmed it fired dozens of missiles of different types, as well as "important test-fire of ballistic missile to verify the movement reliability of a special functional warhead paralyzing the operation command system of the enemy."

A drill involving around 500 fighters, where two tactical ballistic missiles and two super-large multiple launch missiles were fired, also took place, according to the report.

"The more persistently the enemies' provocative military moves continue, the more thoroughly and mercilessly the KPA will counter them," the report said.

The joint US-South Korea drills ended on Saturday after six days.

North Korea has been testing missiles at an unusually high frequency, including what South Korea believes to be an intercontinental ballistic missile with a range of several thousand miles and capable of carrying nuclear warheads. Observers fear that Pyongyang's first nuclear test in years is imminent.

UN resolutions prohibit North Korea from testing ballistic missiles of any range.