SEOUL, South Korea — Raising tensions with South Korea yet again, North Korea today cut its last military hot line with Seoul, a link that has been essential in operating the last major symbol of inter-Korean cooperation: an industrial complex in the North that employs hundreds of workers from the South.

There was no immediate word about what cutting one of the few remaining official North-South links would mean for South Korean workers who were at the Kaesong industrial complex. When the link was last cut, in 2009, many South Koreans were stranded in the North.

The hot line shutdown is the latest of many threats and provocative actions from North Korea, which is angry over U.S.-South Korean military drills and recent U.N. sanctions punishing it for its Feb. 12 nuclear test. In a statement announcing the shutdown, the North repeated its claim that war may break out any moment.

South Korean officials said that about 750 South Koreans were in Kaesong today, and that the two Koreas had normal communications earlier in the day over the hot line when South Korean workers traveled back and forth to the factory park as scheduled.

The hot line is used by the two countries’ militaries to arrange border crossings by the workers.