North Korea's military has ordered artillery units along the border with South Korea to be fully ready to open fire, state media has reported, after the North warned of a "horrible disaster" over the alleged flight of drones over its capital.

North Korea's defense ministry issued the statement Sunday night, days after the recalcitrant regime claimed South Korea had sent unmanned drones carrying anti-North Korea propaganda leaflets over Pyongyang three times this month.

"The Korean People's Army issued a preliminary operation order Oct. 12 to the combined artillery units along the border and the units taking on an important firepower task to get fully ready to open fire," read the statement carried by the Korean Central News Agency.

The military ordered eight artillery brigades fully armed in a wartime mode to be on standby to open fire, and reinforced anti-air observation posts in Pyongyang, it said.

"We warn repeatedly that we will take action according to our judgment, regarding any drones to be spotted again as the ones from the ROK and deeming it a declaration of war," a spokesperson at the defense ministry said in a separate statement, using the acronym of South Korea's official name, the Republic of Korea.

North Korea claimed Friday that it detected South Korean drones carrying anti-North Korea leaflets in the night skies over Pyongyang three times this month and threatened to respond with force if such flights occur again.

Kim Yo-jong, the powerful sister of North Korean leader Kim Jong-un, warned Saturday that South Korea will face a "horrible disaster" in case such drones are flown again into the North.

She issued a similar back-to-back statement Sunday night, calling on South Korea's military to come up with measures to prevent the recurrence of violating North Korean airspace.

In response to North Korea's military threat, South Korea's defense ministry warned Sunday that the North will face "the end of its regime" if it causes any harm to South Korean people. The South Korean military has said it could not confirm whether the North's drone claims were true.

South Korea's unification ministry said Monday North Korea may have made an "abrupt" claim over the alleged drone infiltration to bolster its internal solidarity and take a firm grip on its people by ratcheting up tensions with South Korea.

"(With the drone assertion), North Korea also could aim to use an excuse to stage provocations or create anxiety and confusion in our society," Koo Byoung-sam, spokesperson at the ministry, told a press briefing.

"Whatever North Korea's intentions are, the North will not gain what it wants through intimidation and provocations," he warned.

Last week, North Korea announced it will cut off all roads and rail links connected to South Korea, its "primary hostile state and invariable principal enemy," and build front-line defense structures.

Since the Rodong Sinmun, North Korea's main newspaper targeting domestic audience, carried a rare report about the purported drone flights over Pyongyang on Saturday, North Korea has ramped up its sharp-tongued rhetoric against South Korea by using state media. (Yonhap)