Hong Kong police have arrested 150 people in a three-day crackdown on an illegal bookmaking syndicate that handled more than HK$320 million (US$40.8 million) in wagers, as officers warned against unlawful betting during the Fifa World Cup.

About 600 officers carried out raids across the city between Friday and Sunday, targeting factory units in Kwai Chung, Tsing Yi, Sha Tin, Kwun Tong and Kowloon City, the organised crime and triad bureau said on Tuesday.

The operation shut down four bet-processing centres, three promotion and administration hubs, and a recruitment venue for illegal gamblers.

Eight websites offering football, horse racing and other sports betting were targeted and are believed to have been aimed at Hong Kong gamblers. Individual wagers ranged from HK$10,000 to HK$300,000.

“Police are urging the public not to take part in any illegal gambling during the World Cup, which is a peak period for unlawful betting,” superintendent Au Yeung Tak of bureau said.

“Anyone placing wagers with an [illegal] bookmaker, whether the bets are taken inside or outside Hong Kong, is committing an offence,”