Patched members of the Mongols gang have been blocked entry to New Zealand, ahead of their fifth-anniversary event in Christchurch this weekend

Immigration New Zealand and Police have been monitoring their attempts to come into the country.

Police say they're keeping a close tab on the gang, and raided a fortified property in Wainoni yesterday.

Canterbury District Commander Tony Hill says three people - aged between 23 and 26 - have bee arrested, on will face charges relating to suspected stolen property.

Hill says unlawful activity won't be tolerated, and police will respond to incidents as they arise.