North Korea repeated its threat on Saturday to shoot down loudspeakers the South has set up at the border to broadcast anti-Pyongyang propaganda messages.
The Korean peninsula has been on edge since the sinking of a South Korean warship off the western coast, killing 46 sailors, in late March.
Seoul has accused the North of torpedoing its navy corvette, the Cheonan.
In what it called a "crucial declaration", North Korea's army general staff said it would shoot down the loudspeakers and all other means of psychological warfare if South Korea resumes its propaganda broadcasts.
"From a military point of view that a psychological warfare is one of the basic operational forms for carrying out a war the installing of such means for the above-said warfare is a direct declaration of a war against the DPRK," the North's official KCNA news agency said, referring to the Democratic People's Republic of Korea.
The heightened tensions and exchanges of rhetoric have rattled Seoul's financial markets, pushing foreign investors already jittery over Europe's debt crisis out of South Korean assets.
South Korea announced punitive measures over the incident in May, including the installation of loudspeakers to resume broadcasts of propaganda messages against Pyongyang. It has yet to start such broadcasts.
"The revolutionary armed forces of the DPRK will launch an all-out military strike to blow up the group's means for the psychological warfare against the DPRK," Saturday's KCNA statement said, repeating similar threats made in recent weeks.
It warned South Korea that any military action on its part would risk turning Seoul "into a sea of flame".
South Korea has said it would be able to contain any military action by the North.
Seoul's Yonhap news agency quoted officials from the South's joint chiefs of staff as saying there were no unusual movements spotted along the border.
ReutersLast Mod: 12 Haziran 2010, 13:26