A Malaysian court on Monday sentenced a teenager to prison for killing 23 people in a fire that he started at a boarding school in September 2017.

The arson incident was termed as one of the worst such tragedies in the country in two decades.

The defendant was 16 at the time of the fire which killed 21 teenage boys and two teachers in the capital Kuala Lumpur and sparked calls for tougher regulation over safety in privately-run schools.

The teenage boy was found guilty of a conspiracy to commit murder. Reuters reports citing a high court judge that he would not be subject to the death penalty because he was a minor when he committed the crime. The defendant's identity was withheld for the same reason.

After the shocking incident in 2017, media reports at the time said the only door to the school's dormitory had caught fire and metal bars on the windows had trapped the boys.

According to the Reuters report, the defendant's lawyer, Haijan Omar, said his client was sorry for what had happened and would appeal the decision.