(THE NEW PAPER) - An Australian man sexually abused dozens of boys, some as young as 10, while working in Singapore from 2000 to 2017.

Labelled as one of Australia's worst sex offenders, Boris Kunsevitsky, 52, travelled through South-east Asia and exploited at least 47 young boys, including some in Singapore.

He took more than 3,300 photographs and videos of himself performing sexual acts with at least 25 of his victims and distributed them online.

His victims were aged 10 to 15. Most were children living in poverty in the Philippines. The exact number of his victims in Singapore is not known. Others included a boy in Indonesia and another in Australia.

Yesterday, Kunsevitsky pleaded guilty to a long list of charges, including 25 counts of having sex with children outside Australia and 12 counts of getting a child to have sex with another child.

The Supreme Court of Victoria in Melbourne heard that he travelled so frequently he filled up several passports and caused untold damage to his victims on his trips.

Kunsevitsky was born in Russia and moved to Australia when he was 12. The website of Melbourne newspaper The Age reported that Singapore was his "adopted home".

The court heard that German police started investigations after finding videos Kunsevitsky had circulated online.

They later alerted their Australian counterparts who began investigating Kunsevitsky in 2016 while he was in Singapore.

They arrested him after finding child exploitation material on his phone when he returned to Melbourne to visit his family in 2017. They then shipped his possessions from Singapore to Australia and found his catalogue of vile material, which showed him having sex with boys or having them perform sex acts on each other.

In some recordings, he was heard telling his victims to smile and relax when they appeared to be in pain, the court was told. His earliest video was dated 2001.

His laptop and two hard drives were found to contain more than 37,000 child porn images that he had downloaded from the Internet.

The court heard that Kunsevitsky, who was diagnosed with a paedophiliac disorder after his arrest, travelled regularly through South-east Asia under the guise of work in sales roles, and later for a medical equipment company, but instead used the trips for sex tourism.

His lawyer, Mr Ian Crisp, disputed the seriousness of his client's crimes by claiming the boys in the videos were "simulating" pain.

Prosecutor Krista Breckweg said the claims showed a lack of remorse and called the acts "depraved and despicable".

Kunsevitsky's last job in Singapore was as technical director of aesthetics products company Esthemedica, which he joined in November 2014.

A spokesman for the company told The New Paper their working relationship has since been terminated.

"Certainly we do not condone such ill intentions or criminal acts against children," he said.

"Our knowledge of him and his character is limited to what we know of him as an employee and his performance in delivering the targets. We had no knowledge of his criminal acts against children whatsoever."

The spokesman also said Kunsevitsky had lied to them, claiming to have returned to Australia for medical reasons.

"We want to emphasise that the company does not condone such appalling acts against children or any individual for that matter," he said.

"Our sympathy goes to all victims and their families who fell prey to his criminal acts."

A character reference by Kunsevitsky's employer, who was not named, was presented in court yesterday.

Mr Crisp said the employer had not been informed of his client's crimes and made the reference knowing only that he was before the court.

Kunsevitsky, dubbed by Australian media as one of the country's worst sex offenders, faces decades in jail. He is in remand pending sentencing.

When contacted yesterday, Singapore police said they are in touch with the Australian authorities and will "render the necessary assistance within the ambit of our laws and international obligations".