North Korea threatened Wednesday to shut a border crossing and open fire on loudspeakers if South Korea makes good on its vow to blare out propaganda across the frontier in revenge for the sinking of a warship. US Secretary of State Hillary Clinton flew to Seoul to show Washington's "rock-solid" support for its ally amid the rising tensions, and said the world had a duty to respond to the North's torpedo attack.
After a weeks-long multinational probe into the sinking of a South Korean corvette on March 26, investigators said they found overwhelming evidence that a North Korean submarine was to blame. The findings into the attack which killed 46 young sailors sparked strong international condemnation of the hardline communist state.
The South Monday announced a package of reprisals, including a halt to most trade and a resumption of the loudspeaker broadcasts suspended six years ago. It is also mounting a diplomatic drive to punish the North through the United Nations Security Council, although veto-wielding member China, the North's sole major ally, is reluctant to sign up.