A California sex offender convicted in the US earlier this year of assaulting underage girls in Cambodia could face 70 years in prison, according to a US news report.

Prosecutor David Herzog told ABC News in Los Angeles that he had requested the maximum sentence be increased from 30 years to 70 years after defendant Ronald Boyajian was convicted of three separate crimes in a Los Angeles court.

Four of his victims produced additional testimony during a sentencing hearing on Monday, the report said, with one of them begging the court “do not allow this man to leave prison”.

In addition to sexual assault of a child, Boyajian was convicted of travelling with the purpose of engaging in illegal sexual acts and committing a felony involving a minor while being required to register as a sex offender. Boyajian was only facing charges for the first crime in Cambodia.

Boyajian committed the crimes between 2002 and 2009 in the “Kilo 11” suburb of Phnom Penh.

Sam Onn, Boyajian’s attorney in Cambodia, yesterday told the Post his client had been treated unfairly.

“According to Cambodian law, he should be serving a sentence here if proven guilty,” Onn said, explaining that Boyajian’s sentence would have been shorter if served in Cambodia.

The accused was arrested with cooperation from the NGO Action Pour les Enfantes (APLE) before being extradited to the US in 2009.

“No defendant is more deserving of a functional life sentence than Ronald Boyajian,” ABC reported Herzog saying in court sentencing papers.