South Korea’s military said Wednesday it had stepped up border propaganda broadcasts targeting North Korean soldiers in protest at Pyongyang’s rocket launch.

South Korea's military said Wednesday it had stepped up border propaganda broadcasts targeting North Korean soldiers in protest at Pyongyang's rocket launch.

The army since last month has blasted across the heavily-fortified border a mix of news, propaganda messages and K-pop music using giant banks of loudspeakers, in response to Pyongyang's fourth nuclear test on January 6.

It deployed more loudspeakers -- mounted on moving vehicles -- along the frontier after the North's rocket launch on Sunday, a defense ministry spokesman told AFP.

"We have deployed more loudspeakers to the border and are airing the broadcast for longer hours every day since then," the spokesman said without elaborating further.

The military reportedly airs the broadcast -- hated by Pyongyang which last year threatened to open fire on the loudspeakers -- about six hours a day.

The rocket launch, widely seen as a disguised long-range missile test, sparked international fury and prompted an agreement at the UN Security Council to slap new sanctions against the increasingly defiant state.

The propaganda broadcasts targeting North Korean troops have been turned on and off in line with the swings of volatile inter-Korea ties.

Seoul last August resumed them for the first time in 11 years after two of its border patrol soldiers were maimed by mines it said was planted by the North's soldiers.

But the broadcasts came to a halt two weeks later after two Koreas reached an agreement to defuse growing military tension and Pyongyang expressed regret over the mine explosion.

Since the broadcasts resumed in January, the North responded by airing its own propaganda towards the South using similar massive batteries of loudspeakers along the border.