The warning comes as Seoul and Washington are set to carry out their annual Ulchi Freedom Shield exercises, aimed at containing the nuclear-armed North, from August 18 to 28.

North Korea -- which attacked its neighbour in 1950, triggering the Korean War -- has always been infuriated by US-South Korean military drills, decrying them as rehearsals for invasion.

"The armed forces of the DPRK will cope with the war drills of the US and (South Korea) with thoroughgoing and resolute counteraction posture... at the level of the right to self-defence," North Korean defence chief No Kwang Chol said in a statement carried by the Korean Central News Agency.

The US stations around 28,500 troops in South Korea, and the allies regularly stage joint drills they describe as defensive in nature.

Seoul and Pyongyang have recently appeared to be heading towards a thaw in relations, with the two sides removing propaganda loudspeakers along the border.

Seoul has said North Korean troops have begun dismantling loudspeakers used to blare unsettling noises along the border, days after Seoul's new administration dismantled ones it used to broadcast propaganda.

The two countries had already halted broadcasts along the demilitarised zone, Seoul's military said in June, after the election of President Lee Jae Myung, who is seeking to ease tensions with Pyongyang.

Relations between the two Koreas had been at one of their lowest points in years under former president Yoon Suk Yeol, with Seoul taking a hard line towards Pyongyang, which has drawn ever closer to Moscow in the wake of Russia's invasion of Ukraine.

Lee has taken a different approach to dealing with the North since his election, including requesting that civic groups cease sending propaganda leaflets over the border by balloon.