South Korea presidency office condemns landmine attack

South Korea's presidential Blue House demanded an apology Tuesday from North Korea as military tensions surged after two border patrol soldiers were maimed by landmine blasts blamed on Pyongyang.

President Park Geun-Hye's spokesman Min Kyung-Wok said the North was responsible for a gross act of provocation that constituted a "clear breach" of the armistice agreement that ended the 1950-53 Korean War.

South Korea says North Korean soldiers sneaked across the border and laid the mines, three of which were tripped by members of a South Korean border patrol last Tuesday.

One soldier wounded in the blasts underwent a double leg amputation, while another had one leg removed.

The incident came with cross-border tensions already running high ahead of the launch next week of a major South Korea-US joint military exercise condemned by Pyongyang.

Because the 1953 armistice was never replaced with a peace treaty, the two Koreas remain technically at war, and North Korea denounces the annual joint drills as provocative rehearsals for invasion.

In response to the mine blasts, South Korea resumed border propaganda operations after a break of more than a decade, switching on batteries of powerful loudspeakers to blare out messages denouncing border provocations.

North Korea is extremely sensitive to such campaigns. The last time the South threatened to turn the loudspeakers back on -- in 2010 -- the North vowed to shell the units involved.

Blue House spokesman Min said the North Korean leadership had to take full responsibility for the mine blasts.

"We sternly urge North Korea to apologise for this provocation and punish those responsible," he said.

The South's defence ministry declined to comment on how many units were involved in the propaganda broadcasts which resumed late Monday afternoon, but media reports suggested loudspeakers had been switched on at up to 11 locations along the border.

The Yonhap news agency reported that military defences were being ramped up and local farmers told to leave their fields in case of North Korean retaliation.

According to a defence ministry official, the messages being boomed across the border -- with an audible range of 10-20 kilometres (6-12 miles) depending on the time of day -- ranged from snippets of world news and the weather forecast to the superiority of democracy.

Both Koreas discontinued the high-decibel propaganda exchanges in 2004 during a period of rapprochement.

But South Korean civil activists have continued -- much to Pyongyang's fury -- to send anti-North leaflets over the border using helium balloons.