North Korea threatened Monday to fire cannons or missiles at anti-Pyongyang leaflets sent from South Korea, amid growing military tension on the peninsula over ongoing joint military drills between Seoul and Washington.

"(North Korea) will aim at and attack any balloons or unmanned drones carrying leaflets," said North Korea's propaganda website, Uriminzokkiri. "We don't hide that the (future) response could be not just a few shots of gunfire but it could be cannons or missiles."

The heightened threat against such leaflet scattering by South Korean activists came amid escalating tension on the Korean Peninsula.

Earlier in the day, the North fired two short-range missiles into the East Sea in protest against the start of the joint Key Resolve-Foal Eagle military exercises.

South Korea is the only country that has scattered such leaflets insulting the dignity and regime of a receiving nation, the website said, adding that the launch of anti-Pyongyang leaflets during the South Korea-U.S. military drill amounts to triggering a war.

The North has strongly protested leaflet launches by some South Korean activists, sometimes firing back at such campaigns that were launched from a border town in the South.

"Leaflet scattering is a clear war aggression in the international law," Uriminzokkiri said, threatening that all the responsibility for such campaigns will be taken by the South.

Despite prolonged inter-Korean feuding over the leaflet issue, the South Korean government has largely remained inactive, saying that the campaign is part of the activists' right to free speech.

The rival Koreas remain technically at war after the 1950-53 Korean War ended in a truce, not a peace treaty.(Yonhap)