North Korea's defense ministry says it has ordered artillery units near the border with South Korea to get ready for further drone invasions by the South.

The ministry made the announcement on Sunday through the state-run Korean Central News Agency.

It reiterated its claim that South Korea sent drones over the capital, Pyongyang, earlier this month and scattered propaganda leaflets.

The ministry said the General Staff of the Korean People's Army gave the order on Saturday to artillery corps near the border.

It also said that eight artillery brigades had been ordered to turn to fire readiness positions by 8 p.m. Sunday, local time, and air surveillance over Pyongyang had been enhanced.

Kim Yo Jong, the sister of North Korean leader Kim Jong Un, also issued a statement on Sunday, stressing the need to immediately stop a recurrence of provocative acts that infringe on the other's territorial airspace.

The South Korean military says it could not confirm whether the North's claims were true. It asked Pyongyang to exercise restraint and said it would retaliate if the safety of South Koreans is endangered.

A senior South Korean government official said in a television program on Sunday that the series of moves by North Korea is being used to apply pressure on the South and to tighten discipline inside the North.