In 2004, the rival Koreas ended decades of propaganda campaigns as relations warmed following a landmark summit in 2000. However, South Korea resumed radio broadcasts to the North last month and installed a dozen propaganda loudspeakers along the border. The resumption of psychological warfare was part of punitive steps taken against the North over the deadly sinking of a South Korean warship.

South Korean Defense Minister Kim Tae-young told a parliamentary hearing Friday that loudspeaker broadcasts would begin after the U.N. Security Council decides on any new measures against the North, Yonhap news agency reported.

South Korea has officially asked the Security Council to punish North Korea for what Seoul says was a North Korean torpedo attack on the 1,200-ton Cheonan warship that killed 46 sailors.

A multinational investigation led by South Korea concluded last month that North Korea was responsible. North Korea has denied responsibility and threatened to respond to South Korean retaliatory measures with war.

The General Staff of the Korean People’s Army said in a statement Saturday that North Korea would launch an “all-out military strike” to blow up any propaganda facilities along the border, and that its retaliation would be “a merciless strike foreseeing even the turn of Seoul … into a sea of flame.”

The statement was carried by the official Korean Central News Agency.