Singapore: An Indian-origin former national serviceman with the Singapore Police Force was sentenced to two years' jail on Tuesday for preying on underage girls online and involving them in sexual acts.

A R Arun Prashanth, 25, committed sexual acts on three of his five victims who were then aged 12 to 15, and was found to have snapped more than 700 upskirt photos of unknown women with his mobile phone, the Straits Times reported.

Before handing down the sentence, District Judge Kessler Soh told him: "I hope you realise that what you had done had caused serious harm to the five young girls."

On July 31, Arun, who is now jobless, pleaded guilty to one count each of sexually penetrating a minor, performing an obscene act on her and procuring the commission of an obscene act by another underage girl. He also admitted to four counts of insulting a woman's modesty. These seven charges involved two minors and four unknown women.

Twenty-one other charges for similar offences involving three other young girls and several unknown women were considered during sentencing. The victims cannot be named due to a gag order, the report said.

Sometime between February and March 2016, Arun sent a message to a 12-year-old girl through Instagram and they exchanged mobile phone numbers when she responded in April that year.

He started sending her lewd messages several times a day soon after. The court heard he had also told the girl on at least two occasions that he was a policeman.

Deputy Public Prosecutor Kwang Jia Min said: "The accused pestered her for naked pictures or videos of herself showering. He also pressed her to meet him at his house or hotels for 'cuddles' or sexual intercourse. (The girl) felt harassed by the accused and she would try to ignore him. However, she would feel bad for not replying and she replied at times."

The girl relented on May 8, 2016 after he repeatedly harassed her.

The DPP said that the girl later regretted giving in to his request and felt depressed.

Arun got to know another girl through a WhatsApp group chat in 2016 and messaged her separately in October that year. He told the 14-year-old that he was from the Home Team (also considered as part of police force) and she told him her age when he asked for it.

He pestered her to meet up but she rejected him and later blocked him on WhatsApp as she found his messages "very annoying". Despite this, Arun continued to send her messages through Instagram, the court heard.

On February 3, 2017, she sent Arun a text message, telling him that she would be playing truant and he invited her to his home in Hume Avenue near Upper Bukit Timah Road in suburb northern Singapore.

When she arrived, he took her to his bedroom and performed an obscene act on the girl.

The court heard that the driver noticed the teenager was trembling and asked her about what had happened. She told him about her ordeal and he drove her to Sembawang Neighbourhood Police Centre to lodge a report.

Officers arrested Arun at his home the next day and they uncovered 720 upskirt photographs of unknown women on his mobile phone during an investigation.

Urging the judge to sentence Arun to at least two years' jail, DPP Kwang said that he had stripped his 12-year-old victim of her innocence, causing her to suffer psychological harm.

Arun's lawyers Edmond Pereira and Harjeet Kaur had stated in their mitigation plea that their client was a first-time offender and asked the court to sentence him to 20 months' jail.

Offenders convicted of sexually penetrating a minor can be jailed for up to 10 years and fined.