The father of the man described as the most prolific rapist in British legal history has said his son’s punishment of life in jail “fits his crimes”.

The first comments from Reynhard Sinaga’s immediate family came as more of his potential victims approached police following his sentencing on Monday to life imprisonment, with a minimum term of 30 years.

The 36-year-old’s father, Saibun Sinaga, told the BBC in a phone call: “We accept the verdict. His punishment fits his crimes. I don’t want to discuss the case any further.”

Greater Manchester police opened a dedicated major incident hotline following the sentencing of Sinaga, a PhD student from Indonesia.

He has been convicted of 136 rapes and sexual offences against 48 young men over two-and-a-half years but police believe he may have assaulted at least 195 men over a longer period.

Sinaga lured his victims back to his flat in Manchester city centre under the guise of being a good Samaritan before drugging them and attacking them after they had passed out.

Detectives said on Tuesday that there had been multiple calls to its major incident hotline since the sentencing and that some of these were from potential further victims of the student.

Although police declined to disclose specific numbers, the force said its incident room had received a “very positive response”.

Duncan Craig, the chief executive of the charity Survivors Manchester, which is supporting some of Sinaga’s victims, said he understood that “about 30 calls” had been made to the hotline although it was unclear how many of those were from potential further victims.

He said: “In my office there’s people ringing up who aren’t directly affected by this particular case but are people who have been sexually assaulted, maybe even in childhood, feeling that now is the time to talk.”

Craig, a trained therapist, said the men abused by Sinaga would be feeling a combination of relief and shock now their abuser had been unmasked, following four trials which imposed reporting restrictions preventing the cases from being made public.

He told the BBC’s Victoria Derbyshire programme: “Everything becomes much more of a reality now.

“Particularly survivors will talk about when a case has concluded there’s this momentary euphoria of ‘Oh thank goodness, that’s it, it’s over’ and then the sudden realisation of ‘Now the work starts to build my life back up’.”

Sinaga, who arrived in Britain on a student visa in 2007, was convicted of 159 offences against 48 young men between January 2015 and June 2017, when he was arrested after one of his victims regained consciousness during an assault.

Police believe he attacked at least 195 victims, including the 48 whose cases were brought to court, judging by the number of “trophies” the rapist kept following his assaults, including video footage, wallets, watches, mobile phones and ID cards. All but four of the 48 victims he assaulted were raped.

Sinaga was jailed for a minimum of 30 years on Monday. The judge, Suzanne Goddard QC, described him as a “dangerous, deeply disturbed and perverted individual” who would never be safe to be released.

Greater Manchester police said anyone with information relating to Sinaga could contact 0800 092 0410 (calls made from within the UK) or 020 7158 0124 (international calls) or make a report online. Anyone affected by the case and needing support from specialist agencies can contact 0800 056 0154 (calls made from within the UK) or 020 7158 0011 (international calls).