A 22-year-old man initially given two years of probation for a spate of sexual attacks on five girls was yesterday given a harsher sentence by the High Court after an appeal by the prosecution.

Chief Justice Sundaresh Menon, who allowed the appeal, noted that the gravity of the offences committed by Ng Lin Kun called for a high degree of deterrence, which justified a reformative training stint.

Over a five-month period in 2013, Ng had used force against five girls - the youngest aged only 10 - to molest them in HDB estates.

The district judge who granted Ng probation in November 2014 had taken into account the molester's low intellectual ability, but CJ Menon found that undue weight was placed on this factor.

There was nothing to indicate that Ng's borderline IQ of 75 had impaired his ability to appreciate the wrongfulness of his actions or to control his impulses, the Chief Justice said.

An Institute of Mental Health report said that after molesting each victim, Ng fled the scene because he knew what he did was wrong.

Ng was a newly married full-time national serviceman when he molested five girls in Jurong West and Choa Chu Kang between March and July in 2013. His first victim was a 10-year-old, who rejected his requests to befriend and to hug her. He grabbed her from behind and pulled her near a rubbish chute area, where he groped her.

The following month, he was in a lift with a Secondary 2 student, who ignored his attempts to befriend her. Before she could walk away, he hugged her, grabbed her breast and kissed her on the cheek.

In July, he followed a 17-year-old polytechnic student into a lift and molested her.

In June 2014, Ng pleaded guilty to outraging their modesty.

The prosecution had wanted him to be sent for reformative training, a strict regime in which young offenders are put behind bars for between 18 months and three years.