SEOUL, South Korea — North Korea, reiterating that it considered the Korean Peninsula back in “a state of war,” threatened Saturday to shut down a factory complex it jointly operates with South Korea and that stands as the last significant symbol of cooperation.

The industrial park, the eight-year-old Kaesong complex in the North Korean border town of the same name, is a crucial source of badly needed cash for the heavily sanctioned North. It funnels more than $92 million a year in wages for 53,400 North Koreans employed there, and its operation has survived despite years of military tensions. The latest threat to close down Kaesong came amid a torrent of bellicose statements by the North in recent days, widely seen as a strategy to increase pressure on South Korea and the United States to soften their policies on the North.

Although South Korean officials reasserted that they were ready to retaliate if the North committed any military provocations, they said they saw no imminent sign of any such attacks. On Saturday, cross-border traffic operated as normal, allowing hundreds of South Koreans to travel to and from Kaesong.

Over 300 South Koreans remained in the complex, where 123 South Korean textile and other labor-intensive factories employ the North Korean workers, at an average monthly wage of $144.