A teenager already serving a probation sentence at a children's home for performing sexual acts on a minor reoffended when he preyed on a 14-year-old boy there.

For performing consensual sexual acts on the minor, the offender, now 18, was sentenced to 18 months' probation yesterday.

He pleaded guilty last month to two counts of sexual penetration involving the underage boy. A third charge for a similar offence was considered during sentencing.

The offender's name as well as details of the home cannot be revealed due to a gag order to protect the victim's identity.

As part of his sentence, the offender must perform 40 hours of community service and his mother posted bond of $5,000 to ensure his good behaviour.

The Straits Times understands that he is not serving his probation in a home, and is working in a cafe.

Deputy Public Prosecutor Asoka Markandu said the first incident at the children's home occurred at around 10pm on Oct 9, 2016, while the two teens were in the living room. The victim did not resist at first but he later tried to push the older boy away.

The next day, the pair had sex in a toilet cubicle in Nex shopping mall. At around 6.30pm that day, the head of the home's social work department called the police. Court documents did not say how he came to know about the offences.

For each count of sexual penetration involving a minor, the older teen could have been jailed for up to 10 years and fined.