The Sun Yee On triad society is spearheading a push by Hong Kong gangsters into Japan, where police are concerned at a recent rise in violent organised crime and drug running.
A South China Morning Post investigation found the gang, which is the largest in the SAR, is forming alliances with the biggest Japanese organised crime group, the Yamaguchi-gumi.
Credit card and passport forgeries, robberies of jewellery shops and designer clothes from department stores, drug running and burglaries were the main activities of Hong Kong triads, police and Chinese crime experts said.
Hong Kong triads are a small element of the foreign gangster scene, which is dominated by Shanghainese, Beijing and Fujian groups, but their sometimes daring crimes are gaining the attention of police.
The number of foreign crime cases involving Hong Kong people has boomed this year, up 25 per cent to 229 cases in the first six months from 184 cases last year. But the number of SAR people involved had dropped from 44 to 33, according to National Police Agency statistics.
This rivals a big rise in cases involving mainland Chinese, up 34 per cent to 7,429.