South Korea has begun to pull out its last remaining workers from a factory zone in North Korea, bringing cross-border cooperation to a complete halt.
The withdrawal, planned to begin on Monday, raises the prospect of the permanent closure of the Kaesong complex, the last point of contact between the two Koreas and a major source of income for isolated Pyongyang.
Operation in the joint industrial zone, established in 2004, have been suspended since early April when North Korea barred South Korean factory managers and supply trucks from entering the park and withdrew all its 53,000 workers amid tension with Seoul and Washington.
Tension on the Korean peninsula has been heightened by nuclear war threats from the North and has led to a flurry of diplomatic efforts seeking to resolve the crisis.
South Korea began pulling out its nationals from Kaesong on Saturday after Pyongyang rejected its dialogue offer.
Al Jazeera's Harry Fawcet, reporting from Seoul, said: "This is the worst crisis that has ever befallen this industrial complex since it opened in 2004."
He said the 50 workers who were leaving were largely infrastructure employees responsible for electricity, water and telecommunications.
South Korean companies with factories at the site have expressed shock at the sudden evacuation, which saw 126 workers return on Saturday in dozens of vehicles loaded with assembled goods and other materials.
"We notified the North about the planned return of 50 people today but have not received approval from the North yet," Unification Ministry spokesman Kim Hyun-seok told reporters.
'Window of dialogue'
Yun Byung-se, the South Korean foreign minister, told a forum in Seoul on Monday that "the window of dialogue is still open" on Kaesong, according to the South's Yonhap news agency.
"North Korea must understand that its missile and nuclear programmes are just an empty dream," Yun added.
But some observers believe a shutdown of the complex would be permanent as the factory equipment there would fall into disrepair and the firms would soon lose their customers.
The complex lies 10km inside the North, which remains technically at war with the South after the 1950-53 Korean War was concluded with a ceasefire rather than a peace treaty.
The North on Monday renewed its own threat of "final and decisive" action on Kaesong if the situation worsened.
The pullout is "a cunning and mean-spirited trick aimed at passing blame to the North for the plight of the complex", said an editorial in the North's ruling communist party newspaper, the Rodong Sinmun.
"The enemy forces should know clearly that we, as warned already, will take any final decisive and crucial measures if they continue to try to aggravate the situation," it said.
Yonhap reported on Sunday that North Korea appeared to be preparing for a major live-fire military exercise on its west coast involving artillery units and air force jets.
Joint South Korea-US military drills which have angered the North are due to end on Tuesday.