The powerful sister of North Korean leader Kim Jong Un accused South Korea on Saturday of deliberately avoiding responsibility for the alleged flights of South Korean drones over the North’s capital, and warned of a “terrible calamity” if they continue.

The statement by Kim Yo Jong came a day after North Korea’s foreign ministry claimed that South Korean drones carrying anti-North Korean propaganda leaflets were detected in the night skies over Pyongyang on Octber 3, and Wednesday and Thursday this week.

The ministry said North Korean forces will prepare “all means of attack” capable of destroying the southern side of the border and the South Korean military, and respond without warning if South Korean drones are detected in its territory again.

South Korea’s defence minister initially denied the accusation, but the South’s military later adjusted its response, saying it could not confirm whether or not the North’s claims were true.

In comments published through state media, Ms Kim, one of her brother’s top foreign policy officials, said that the South Korean military’s vague statements should be taken as proof that it was “either the main culprit or accomplice in this incident”.

“If the military stood by while its own citizens employed drones, a widely recognised multi-purpose military tool, to violate another country’s sovereignty, thereby increasing the risk of armed conflict with a potential adversary, this would amount to intentional acquiescence and collusion,” she said.

“The moment a South Korean drone is discovered once again in skies above our capital, a terrible calamity will surely occur. I personally hope that does not happen.”

South Korea’s military and government did not immediately respond to Ms Kim’s comments.

Tensions between the Koreas are now at their worst for years as the pace of both North Korea’s missile tests and the South’s combined military training with the United States have intensified in tit-for-tat.

The animosity has been exacerbated by Cold War-style psychological warfare campaigns between the Koreas in recent months.

Since May, North Korea has sent thousands of balloons carrying paper waste, plastic and other rubbish to drop on the South, in what it described as retaliation against South Korean civilian activists who flew balloons with anti-North Korean propaganda leaflets across the border.

South Korea’s military responded to the North’s balloon campaign by using border loudspeakers to broadcast propaganda and K-pop to North Korea.

South Korean army soldiers patrol along a barbed-wire border fence
South Korean army soldiers patrol along the barbed-wire fence in Paju, South Korea, near the border with North Korea (Ahn Young-joon/AP)

North Korea is extremely sensitive to any outside criticism of the authoritarian government of leader Kim Jong Un and his family’s dynastic rule.

South Korean officials have been raising concern that North Korea may seek to increase pressure on Seoul and Washington ahead of the US presidential election in November.

Experts say Mr Kim’s long-term goal is to eventually force Washington to accept North Korea as a nuclear power and to negotiate security and economic concessions from a position of strength.

In written answers to questions by The Associated Press this month, South Korean President Yoon Suk Yeol said North Korea is likely preparing major provocations around the US election, possibly including a test detonation of a nuclear device or flight-test of an intercontinental ballistic missile test.