SEOUL North Korea warned on Monday of unpredictable disaster unless the South and the United States stop allowing tours inside a heavily armed border buffer that is one of the most visited spots on the peninsula.
The warning comes after tensions rose when a South Korean navy ship sank on Friday. Early reports that the North may have been involved spooked markets but Seoul later said it was almost certain Pyongyang had played no part.
A South Korean Defense Ministry official said divers were searching for survivors but were hampered by murky water at the scene near the disputed sea border with the North.
Divers tapped on the tail of the capsized hull where most of the missing were presumed trapped but did not get any response, Brigadier General Lee Ki-sik told a briefing.
Thirty of the 46 missing are non-commissioned officers. The remaining 16 are conscripted sailors.
South Korea's Defense Minister Kim Tae-young told parliament nothing had been ruled out as a possible cause, including the chance the ship was struck by one of the 4,000 North Korean sea mines yet to be recovered after the 1950-53 Korean War.
Other causes mentioned in the parliament session included an internal explosion and the ship hitting underwater rocks. The minister also said there was also a possibility the North deliberately floated a mine into the South, broadcaster SBS said.
North Korea has made no mention of the sinking in its official media but issued a warning about the land border.
"If the U.S. and the South Korean authorities persist in their wrong acts to misuse the DMZ for the inter-Korean confrontation despite our warnings, these will entail unpredictable incidents including the loss of human lives," the North's KCNA news agency quoted a military spokesman as saying.
The Demilitarized Zone is the 4-km (2.5-mile) wide buffer running along the border drawn up under a truce that ended the Korean War, which was fought between U.S.-led U.N. forces with the South against North Korean and Chinese troops.
An unidentified army spokesman of the North's Korean People's Army said South Korea was engaged in "deliberate acts to turn the DMZ into theater of confrontation with the (North) and a site of psychological warfare" by allowing tours inside the border zone.
The warning called on the South to halt tours for journalists to areas of the buffer zone that stretches across the peninsula.
Nearly half a million people a year visit the Panmunjom truce village inside the zone as well as other sites showing aspects of the Cold War's last frontier, more than 170,000 of them from abroad, an official at the Paju city that borders the North said. The North also takes visitors to its side of the border.
The city of Paju and the United Service Organisations (USO), affiliated with the U.S. military in the South, said they had no plans yet to cancel tours.
Financial market players said the incident had a limited impact on share movements, although some defense firm stocks rallied.
(Additional reporting by Rhee So-eui, Christine Kim and Jungyoun Park; Editing by Jon Herskovitz and Nick Macfie)