North Korea has banned the entry of South Koreans to a joint industrial complex in a rare move amid high tensions on the Korean peninsula, the South's Unification Ministry said.
Wednesday's move sparked fears the North could carry out its threatened shutdown of the complex as part of a standoff with Washington and Seoul.
"The North this morning notified us that it will only allow returning trips from Kaesong and will ban trips to the complex," Unification Ministry spokesman Kim Hyung-suk told reporters.
Kim said the North had not specified how long the ban would remain in effect.
The ministry said 861 South Korean workers are in the industrial complex while 179 workers await entry.
Border crossings for Kaesong, which lies 10km inside North Korea, have been functioning normally despite soaring tensions in recent weeks between the North and the South.
'Cash cow'
Al Jazeera's Harry Fawcett, reporting from the South Korean capital, said that historically, "even in the most serious of crises Kaesong has remained opened and remained operational."
A major "cash cow" for Pyongyang, Kaesong brings in $90m annually in wages to 53,000 North Korean workers, he said.
The operating stability of the complex is seen as a bellwether of inter-Korean relations, and its closure would mark a clear escalation of tensions beyond all the military rhetoric.
A shut down of the plant, said our correspondent, would mean "a real deterioration in relations between the two countries."
The latest move comes after North Korea said on Tuesday it would revive a mothballed nuclear reactor able to produce bomb-grade plutonium in a standoff that has seen Washington shift military resources into South Korea.
Pyongyang has been ramping up its threats since it was hit by international sanctions following its third nuclear test earlier this year.
PHOTO CAPTION
North Korea's town Kaepoong is viewed from the unification observation post near the border village of Panmunjom, that has separated the two Koreas since the Korean War, in Paju, north of Seoul, South Korea, Saturday, March 30, 2013.
Al-Jazeera