Reclusive North Korea last week expelled South Korean workers from the Mount Kumgang resort in the latest move in a three-year dispute over what was once a symbol of cooperation between the rival Koreas.

Tours of mostly South Korean visitors to the scenic mountain resort have been suspended since North Korean soldiers shot and killed a South Korean tourist there in 2008, drying up a lucrative source of hard currency for the impoverished North.

“We request that foreign governments and businesses understand steps taken by the North and refrain from tourism projects or investment in the Mouth Kumgang district,” a South Korean Unification Ministry official said.

“North Korea does not have credibility when it comes to investment, and has trouble ensuring the safety of tourists,” the official told reporters.

North Korea has unilaterally suspended the tour operating license given to South Korea’s Hyundai Group and its partner companies, which have invested nearly $320 million, and said it would dispose of their assets.

The North has tried to draw investments in tourism in Kumgang from other countries, notably in China, to maintain the flow of hard cash into the country.

The country has earned $487 million from the resort since it was opened in 1998. About 1.9 million tourists have visited the resort, mostly from the South.

The opening of the Kumgang resort — comprising hotels, restaurants and a golf course — followed a decade-long period of warming ties between the two Koreas, known in the South as the “Sunshine policy” years.

That period ended with the election in South Korea of conservative President Lee Myung-bak in 2008, who declared there would be no aid for the destitute neighbor until the North abandoned its nuclear arms program.

Inter-Korean ties have declined sharply in the past three years, hitting a low last year when 50 South Koreans were killed in two attacks and the North unveiled a uranium enrichment facility.

However, tensions have eased on the peninsula this year and a flurry of diplomacy has raised hopes for a resumption of regional talks on disabling the North’s nuclear program.