North Korean leader Kim Jong Un convened a high-level national security meeting on Monday, state media reported, and ordered a plan for “immediate military action” at a time of rising tensions with the South.

The meeting in Pyongyang was attended by the country's top security officials, including the army chief and other military officials, as well as state security and defense ministers.

“He laid out the direction of immediate military action and pointed out important tasks to be fulfilled in deterring war and exercising the right to self-defense,” the Korea Central News Agency (KCNA) reported.

The meeting comes as the nuclear-armed North has accused Seoul of flying drones over its capital and moving troops to its border. South Korea said on Monday it was “fully prepared” to respond in the event of a shelling.

Officials at the meeting in Pyongyang heard a report of a “serious provocation of the enemy,” KCNA reported, an apparent reference to the drone flights.

Kim “expressed a tough political and military stance” at the meeting, state media said.

The North has accused Seoul of being responsible for the drones that dropped propaganda leaflets full of “inflammatory rumors and nonsense” and warned on Sunday that it would consider a “declaration of war” if another drone was detected.

Seoul's military initially denied being behind the flights. Local speculation has focused on activist groups in the South that have long sent propaganda and U.S. currency north, typically by balloon.

The United Nations command, which oversees the armistice that ended active fighting in the 1950-53 Korean War, said it was aware of the North Korean claim.

“The command is currently investigating the matter in strict accordance with the ceasefire agreement,” it said.

The two Koreas are technically still at war.