North Korea vowed on Saturday to launch an all-out attack against South Korean loudspeakers and other propaganda facilities along their heavily fortified border, warning it can even turn Seoul into a "sea of flame."

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 UN 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.

The North's military earlier warned it would fire at any propaganda facilities installed in the Demilitarized Zone that has separated the two Koreas since the end of the 1950-53 Korean War, which concluded in a truce, not a peace treaty.

South Korea's Defense Ministry and the Joint Chiefs of Staff said they had no immediate comment on the North's latest threat.

North Korea has for years threatened the South with destruction, though it has never followed through with an all-out military assault since the 1953 armistice was concluded.

Seoul, South Korea's capital of over 10 million people, is considered vulnerable because it is well within the range of North Korean artillery.