North Korea on Sunday warned South Korea and the US against any attempt to stage a "special operation" to hit the Pyongyang leadership and military installations, including the nuclear arms base.

A North Korean military statement said it was ready to "mercilessly smash the enemy's moves... now that the sinister aim of the US imperialists and the South Korean War maniacs' 'special operation' to hurt the dignity of the DPRK's (Noth Korea) supreme leadership has become clear, and they disclosed even the dangerous attempt at 'preemptive attack'".

The military accused the US and South Korea of being "busy staging madcap joint military drills for aggression involving more than 300,000 troops, US nuclear carrier Carl Vinson and B-1B and other nuclear strategic assets", Yonhap news agency reported.

"The situation has reached an extreme phase which should not be overlooked," the statement said.

It urged Washington and Seoul to think twice about the catastrophic consequences to be entailed by their outrageous military actions.

South Korea's Joint Chiefs of Staff in a response warned North Korea of consequences of its provocation.

"If the North provokes, our military will sternly retaliate as we have prepared and ensure such an action leads to self-destruction," Army Gen. Lee Sun-jin said in a statement.

On March 13, combined forces of South Korea and the US kicked off the annual command post exercise, following the launch on March 1 of the joint field training drill with the code-name of Foal Eagle.

North Korea has denounced the joint military exercises as a dress rehearsal for northward invasion.

The US-South Korea commands will exercise Operation Plan 5015 during the Key Resolve drill. The operation plan includes preemptive strikes against Pyongyang's nuclear and missile facilities when signs of attack are detected

The military defended Foal Eagle as a defensive training to enhance the alliance's preparedness to defend the South in case of armed conflict. The North has criticised the exercise as preparation for invasion.