North Korea on Thursday denounced South Korea and the United States' latest joint military drills as an "unprecedented" war rehearsal, vowing to take "offensive" military steps against such actions.

In a commentary carried by the Korean Central News Agency, Choe Ju-hyon, a critic of international security affairs, said Seoul and Washington's "frantic" military drills have turned the Korean Peninsula into a "powder keg" that can explode at any moment.

"Our war deterrence will continue to show responsibility and confidence in its critical mission with offensive actions," Choe said.

The North apparently toned down the level of warning by citing remarks by an individual critic, but it still continued to issue nuclear threats against the allies' military exercise.

Choe denounced the US as a "cancer to the world peace" for recently staging trilateral naval exercises with its two Asian allies of South Korea and Japan, involving the USS Nimitz carrier.

South Korea and the US also staged combined air drills, involving a B-52H strategic bomber, Wednesday, amid Pyongyang's provocative acts, such as its unveiling of the Hwasan-31 tactical nuclear warhead and the test of an underwater nuclear-capable attack drone.

The North has long decried the allies' military exercises as rehearsals of an invasion against it and used them as a pretext to bolster its weapons tests.

Observers said the North is expected to intensify provocative acts, such as the firing of a solid-fuel intercontinental ballistic missile or launching of a military spy satellite. (Yonhap)