The police have crushed an organised criminal group and arrested 66 people in simultaneous raids across Singapore on Wednesday.

The 61 men and five women, aged between 17 and 63, were arrested for their suspected involvement in gang-related activities, operating illegal gambling dens and other criminal activities, the police said on Wednesday night.

Officers raided 10 locations and seized cash amounting to $428,720, jewellery, watches, mobile phones and gambling paraphernalia. Bank accounts belonging to the suspects were also frozen by the police to prevent any spending of criminal proceeds, they said.

The locations of the raids included Geylang, Sengkang, Bedok and Ang Mo Kio. Officers from the Criminal Investigation Department, Police Intelligence Department, Special Operations Command, Bedok Police Division, Clementi Police Division and Tanglin Police Division were involved in the operation.

Investigations against all the suspects are ongoing for offences under the Organised Crime Act 2015, Common Gaming Houses Act and Societies Act.

Deputy commissioner of police for investigations and intelligence Florence Chua noted that organised criminal groups are involved in serious criminal activities and can pose a threat to Singapore's safety and security.

"This operation was conducted as part of the police's ongoing efforts to disrupt and dismantle organised criminal groups," she said.

"The police will remain resolute in our enforcement efforts against such groups, so as to keep Singapore safe and secure."

If convicted, the suspects may each face a fine of up to $100,000, a jail term of up to five years, or both.