SEOUL--North Korea is gearing up to send propaganda leaflets over its southern border, denouncing North Korean defectors and South Korea, its state media said on Saturday, the latest retaliation for leaflets from the South as bilateral tensions rise.

Enraged North Korean people across the country "are actively pushing forward with the preparations for launching a large-scale distribution of leaflets," which are piled as high as a mountain, said state news agency KCNA.

"Every action should be met with proper reaction and only when one experiences it oneself, one can feel how offending it is," KCNA said.

North Korea has blamed North Korean defectors for launching leaflets across the border and threatened military action. On Tuesday, Pyongyang blew up an inter-Korean liaison office to show its displeasure against the defectors and South Korea for not stopping them launching leaflets.

South Korea's unification ministry, which is responsible for inter-Korean dialogue, said on Saturday that North Korea's plan to send leaflets was "extremely regrettable," and urged it to scrap the plan immediately.

A North Korean defector-led group said on Friday it had scrapped a plan to send hundreds of plastic bottles stuffed with rice, medicine and face masks to North Korea by throwing them into the sea near the border on Sunday.

The two Koreas, which are still technically at war as their 1950-53 conflict ended without a peace treaty, have waged leaflet campaigns for decades.

South Korea's military used to launch anti-North flyers across the demilitarized zone, but the program ended in 2010.

Several defector-led groups have regularly sent back flyers, together with food, $1 bills, mini radios and USB sticks containing South Korean dramas and news, usually by balloon over the border or in bottles by river.

Pyongyang has used balloons to send its anti-South leaflets. South Koreans previously were rewarded with stationery if they reported leaflets from the North.