Seoul, South Korea ? North Korea lashed out today after the start of joint U.S.-South Korean military exercises, saying the drills were tantamount to war and threatening to take action.

The statement from the North’s Korean People’s Army came a day after the start of the games, mainly computer-simulated exercises.

The developments come amid renewed concern that the communist nation is possibly planning to test a nuclear weapon, following its provocative missile launches last month.

The North – which commonly issues heated statements warning that the peninsula stands on the brink of war – said it “reserves the right to undertake a pre-emptive action for self-defense against the enemy at a crucial time it deems necessary to defend itself.”

In its statement carried by the official Korean Central News Agency, the military also said the drills rendered “null and void” the armistice that ended the 1950-53 Korean War.