Beijing, Aug 27 (IANS): North Korean leader Kim Jong-un has signed an order of battle to counter possible attacks by South Korea and the US, state-run news agency KCNA reported.

During a speech marking the 52nd anniversary of the "military-first revolutionary leadership" of his late father Kim Jong-il, Kim Jong-un said Seoul and Washington are staging large-scale war drills targeting North Korea.

"If the enemies fire even a single shell on our inviolable territory and territorial waters, the Korean People's Army (KPA) should deal prompt deadly blows at them and make an all-out counter-offensive to achieve national reunification," Xinhua quoted Kim as saying.

The KCNA report said Kim examined an operation plan and signed it.

He also asked the army to stay alert against "reckless moves" by the enemies.

Kim, also supreme commander of the army, vowed earlier this month to "turn the west sea into a graveyard of the invaders" during a visit to a front-line artillery unit near the western sea border.

The annual joint drills between South Korea and the US, code-named "Ulchi Freedom Guardian", began Aug 20 and will continue till Aug 31. Around 56,000 South Korean troops and 30,000 US soldiers are involved.