It is the second such incident in two months, after 13 workers at a North Korea-themed restaurant in the Chinese city of Ningbo made a high-profile defection to Seoul in April.

Nearly 30,000 North Koreans have fled poverty and repression at home to settle in the capitalist South.

But group defections are rare, especially by staff who work in North Korean restaurants abroad, which are a key source of hard currency for the regime in Pyongyang.

They are generally handpicked from families that are “loyal” to the regime and go through extensive ideological training before being sent out.

Pyongyang reacted angrily to April’s defection, insisting that the 12 women were tricked by spies from Seoul who effectively “kidnapped” them with the help of a North Korean manager who also escaped.

Seoul says all 13 members of staff defected voluntarily.

The isolated, impoverished North operates a network of more than 100 restaurants abroad where young female workers entertain patrons with singing and dancing.

But many suffered a drop in sales after the United Nations imposed tougher sanctions on Pyongyang following its latest nuclear and long-range rocket tests staged in violation of UN resolutions, according to Seoul’s spy agency.

The UN sanctions do not target the restaurants but Seoul has urged its citizens to avoid them, saying a boycott would block the foreign currency cash flow to the regime.

Overall, North Korea has about 50,000 to 60,000 workers abroad, mostly in Russia and China, with a mission to bring in foreign currency, according to the National Intelligence Service.

The restaurant workers who defected to the South in April have said that their restaurant was struggling to meet demands from North Korean authorities at home for foreign currency, according to Seoul’s Unification Ministry.

Additional reporting by Associated Press