North Korea warned Monday that it will force South Korea to pay a dear price for its criticism of the North's dignity, the latest in a series of verbal threats against the South.

The rival Koreas agreed in February to halt cross-border slander during their first high-level talks in seven years.

Still, the North has since claimed South Korea hurled mud at the North's leadership and its social system with the communist country citing, among other things, anti-Pyongyang leaflets.

For years, North Korean defectors in the South and conservative activists have flown the leaflets to the North via balloons to help encourage North Koreans to eventually rise up against the Pyongyang regime.

The North's military and people will force South Korea to "pay a dear price for insulting our dignity and system," the North's Committee for the Peaceful Reunification of Korea said in comments carried by the country's official Korean Central News Agency.

The committee did not elaborate on what it meant by a dear price.

The North has made several military threats against the South over the leaflets in recent years. The North has also repeatedly pressed South Korea to stop its activists from sending the leaflets.

South Korea has said there are no legal grounds to prevent activists from sending the leaflets, citing freedom of expression.

South Korea recently warned the North against using vulgar language toward President Park Geun-hye. The North has called the female president an "eccentric old spinster" and a "hen" over her comments on North Korea's economic difficulties and its homeless children.

The North's committee also called Park a kingpin of slander for her recent comments critical of the North.

Also on Monday, the North's committee suggested that it has nothing do with three small unmanned aerial vehicles found in South Korea in recent weeks.

South Korea "fabricated the incident on unmanned aerial vehicles in its frantic move to slander the North," said the North's Committee for the Peaceful Reunification of Korea.

The reaction came three days after South Korea said that North Korea sent the drones to the South for spying purposes, citing circumstantial evidence.

The three drones had batteries whose expiration dates were inscribed in the North Korean vernacular, and six fingerprints unregistered in the South Korean database were collected from one of the drones, according to the South's defense ministry. (Yonhap)