SEOUL, South Korea (AP) — North Korea has accused rival South Korea of flying drones to its capital to drop anti-North Korean propaganda leaflets and threatened to respond with force if such flights occur again.

North Korea’s Foreign Ministry said in a statement Friday that South Korean drones were detected on Oct. 3 and Wednesday and Thursday this week.

The ministry accused the South of violating North Korea's “sacred” sovereignty and threatening its security, and said its forces will prepare “all means of attack” and respond without warning if South Korean drones are detected in its territory again.

South Korea's government and military didn't immediately comment on the North's statement.

Tensions between the rival Koreas have escalated in recent months as North Korean leader Kim Jong Un has ramped up weapons tests and threats and South Korea has responded by strengthening its joint military exercises with the United States.

On Wednesday, North Korea said it will permanently block its border with South Korea and build front-line defense structures to cope with “confrontational hysteria” by South Korean and U.S. forces.