North Korea will fire across a land border with South Korea if Seoul continues its anti-North psychological campaign, the North's official media said on Sunday ahead of a joint military drill between the United States and South Korea.

South Korea's military has been dropping leaflets into North Korea about democracy protests in Egypt as part of a psychological campaign and the South Korean military also sent food, medicines and radios for residents in a bid to encourage North Koreans to think about change.

"The on-going psychological warfare by the puppet military in the frontline area is a treacherous deed and a wanton challenge to the demand of the times and desire of all the fellow countrymen to bring about a new phase of peaceful reunification and national prosperity through all-round dialogue and negotiations," KCNA news agency said.

"We officially notify that our army will stage a direct fire at the Rimjin Pavilion and other sources of the anti-DPRK psychological warfare to destroy them on the principle of self-defense, if such actions last despite our repeated warning."

The Rimjin Pavilion is an area in South Korea near the heavily armed Demilitarized Zone (DMZ) which separates the two Koreas.

North Korea will also be on a heightened state of alert for possible provocation during the joint military drill between the United States and South Korea which starts on Monday, KCNA said.

It said North Korea will respond to the planned military drills with "all-out war" if there is any provocation.

Tensions rose on the divided peninsula when 46 sailors were killed in an attack last March on a South Korean naval vessel. North Korea, which has denied responsibility, shelled the southern island of Yeonpyeong last November, killing four people.

Their first attempt at talks broke down earlier in February dealing a setback to plans to resume international disarmament talks with the North.

North Korea has said it wants to return to the broader six-party negotiations, but Seoul and Washington have questioned its sincerity about denuclearizing - pointing to its revelations in November about a uranium-enrichment program.-Reuters