SINGAPORE - A teenager who claimed to have a bomb in his bag while on an MRT train and pretended to detonate it by pressing imaginary buttons was sentenced to 21 months' probation on Monday (May 30).

He had pleaded guilty in court on March 24 to four charges for offences including harassment, theft and rioting.

The teen will have to undergo four months of intensive probation and 17 months of supervised probation, as well as performing 60 hours of community service.

His parents, who were present in court on Monday, are bonded $5,000 to ensure his good behaviour.

The boy cannot be identified as anyone below 18 is covered under the Children and Young Persons Act.

Deputy Public Prosecutor Jason Chua said in court documents that the teenager was on a train heading to Serangoon from Hougang with friends at around 8pm on Dec 26, 2019.

He was seated with his bag on his lap when he said loudly: "Guys, inside my bag (is) the... bomb... So we're going to bomb the whole station, and everybody inside the train (is) going to die."

He then put the sling bag under the train seat, covered his ears and shouted, "Allahu Akbar", an Arabic phrase that means "God is greatest".

Other passengers on the train heard him, and his antics were recorded and uploaded on social media platform Instagram.

In an unrelated incident, one of the teen's friends hatched a plan to steal a gold chain from a Hougang pawnshop, and the boy agreed to take part in the crime.

On Jan 16, 2020, he went to the pawnshop and asked to see its biggest gold chain. When he was handed an item priced at $7,455, he ran off with it. He left the chain in a nearby pavilion, and the friend picked it up about 15 minutes later.

The next day, the chain was sold at another pawnshop for about $6,500. The friend later gave the teenager $150.

Separately, the teenager and several other people ganged up to assault an 18-year-old boy in Hougang in the wee hours of May 2 last year.

After the attack, the victim went to Tan Tock Seng Hospital, where he was found to have injuries including facial wounds.

For harassment, the offender could have been fined up to $5,000.

For theft in dwelling, he could have been jailed for up to seven years and fined.

For rioting, he could have been jailed for up to seven years and caned.