Seven remaining South Korean workers at a joint industrial zone in North Korea have returned home, completing a withdrawal from the complex after months of cross-border tensions.

Seoul's unification ministry said remaining issues had been resolved and the workers crossed back over the border on Friday evening.

The Kaesong industrial complex, built 10 km north of the tense border in 2004, was once a rare symbol of inter-Korean cooperation but now faces the possibility of permanent closure.

South Korea pulled out most of its remaining workers early on Tuesday but the seven stayed to settle unresolved issues such as unpaid taxes and wages for North Korean workers, believed to amount to millions of dollars.

A South Korean vehicle loaded with cash would head to the North at the same time to make the payments demanded by Pyongyang, the South Korean ministry said.

Late last month, Seoul ordered all remaining South Koreans to leave after the North banned entry by southerners, pulled out all its own 53,000 workers and rejected the South's call for talks on the impasse.

Tensions high

Tension has been high since the North, angered by fresh UN sanctions sparked by its nuclear test in February and South Korea-US military drills, issued a series of threats of a nuclear war against Seoul and Washington.

Seoul's top nuclear envoy headed for Beijing on Wednesday for talks with Chinese officials on the stand-off on the Korean Peninsula.

The North ignored a plea by South Korean businessmen to visit the joint industrial zone on Tuesday for talks on its future.

Kaesong is a crucial hard currency source for the impoverished North, through taxes and revenues, and from its cut of worker wages.

The project was born out of the "Sunshine Policy" of inter-Korean conciliation initiated in the late 1990s by South Korean President Kim Dae-jung.

Source: Agencies