A Hamilton man has been arrested for abducting and sexually assaulting men in Hamilton's central city, but police believe there could be other victims reluctant to come forward.



Police arrested a 33-year-old man last night in relation to the sexual assaults of two male hitchhikers in Claudelands early Friday morning and the abduction and assault of a man on Mill St on October 24. The man was arrested following a search of a property in the central city at 7pm yesterday.



Police believe the man has been involved in a number of other related crimes and are urging victims to contact them with more information.



He was to appear in Hamilton District Court today on two counts of abduction, two counts of stupefying a person to commit a crime, four counts of sexual violation and one charge of indecent assault. Police say further charges are likely.



Hamilton CIB detective senior sergeant Karl Thornton said it had been a challenging investigation for police due to the reluctance of victims to discuss the offences.



Police had been investigating the case, named Operation Triangle, since the first complaint on Sunday, October 24.



"We believe the offender may have been involved in other incidents and we also understand the reluctance on the part of victims to come forward.



"Police acknowledge any victims of sexual assault is traumatised by the ordeal but we implore anyone else who may have had contact with this man to come forward." They will be releasing further information later today.



Police are still investigating whether the accused is related to an incident on November 1 when a 25-year-old man was kidnapped for several hours and then raped on the corner of Norton and Rifle Range Rds.



The man said he was taken to a vacant section and subjected to a prolonged sexual assault. At the time Hamilton CIB Detective Sergeant Andy BuBear described it as a totally random attack. However after the November 1 attack, Mike Holloway, of the Male Survivors of Sexual Abuse Trust in Hamilton, suggested the rapist had probably struck before.



Mr Holloway said men were often reticent about reporting sexual attacks and kept them secret. They were far more common than reports suggested. "I can almost guarantee that there will be other incidents that have gone on out there that have gone unreported and chances are this offender has done it before."



Waikato University Associate Professor Doug Boer said male rape victims were even more reticent than women when it came to reporting being sexually assaulted "because of the assault on their self-image as a man as well as being a rape victim".



"Also, men don't generally conceive of themselves as potentially a victim of sexual assault, so when it happens it is entirely counter to the victim's sense of what is possible."



Dr Boer suggested his most "liberal estimate" of adult men being sexually assaulted was about 3 to 4 per cent.