The group was "abducted" by South Korea while working in a Pyongyang-run restaurant in China, a spokesman for the North Korean Red Cross Society said on Tuesday.

The official decried the move as a "hideous crime" targeting the North's "dignity and social system and the life and security of its citizens," according to a statement quoted by North Korea's KCNA news agency.

On Friday, Seoul disclosed that 13 North Korean workers had defected to the South from an unnamed country. Three days later, Beijing announced a North Korean restaurant manager and twelve employees had freely left Chinese territory in accordance with the law. However, Beijing did not confirm it was the same group.

Pyongyang sends tens of thousands of workers abroad on strictly controlled jobs, such as restaurants in China or logging camps in Russia. The North Korean nationals are monitored by special minders and tasked with bringing in hard currency into the isolated country.

Although individual workers have been known to defect, a group of 13 people is unprecedented, according to South Korea.

Feeding the fire

In the Tuesday statement, the North Korean official demanded the citizens' immediate return and an apology from Seoul, and threatened "unimaginable consequences and strong countermeasures" if the state failed to comply.

The latest incident comes at a time of heightened tensions between the states, with Pyongyang claiming breakthroughs in its nuclear weapons programs. In response, the US and South Korea held joint military exercises and led a diplomatic charge to impose new sanctions on the North.

On Monday, Seoul announced that a North Korean colonel in charge of intelligence operations had also deserted the Pyongyang regime sometime last year, describing the man as the "the highest-level military official to have ever defected to the South."

dj/bk (Reuters, AFP)