A heartbroken father has revealed that his five-year-old son died locked in the school van after apparently failing to work out how to exit the vehicle when he was forgotten there by staff.

The incident took place in Johor Bahru, Malaysia, with the victim said to have been trapped in the school van over four hours.

Picture shows the five-year-old boy Yu Zie, undated. He was left in a school bus and died in Johor, Malaysia. Note: Private photo taken from local media. (Newsflash/NX)

The victim has been named as Yu Zie and his heartbroken 37-year-old father Teo Jia said: "I am very distressed.

"The van driver should have properly checked and ensured that all the children had exited before locking the van or going home."

He also accused the school where his son was a pupil of negligence, saying that they should have checked the attendance sheet and verified the child's whereabouts after realising that he was not there.

Picture shows the five-year-old boy Yu Zie, undated. He was left in a school bus and died in Johor, Malaysia. Note: Image is a screenshot from video. (Newsflash/NX)

The dad, who works in Singapore, said that his son was picked up from their home in Taman Bukit Indah at about 7:15 am on the day of the tragic incident.

The van was set to arrive at the school at about 8:15 am, with the driver reportedly leaving the band nearby after dropping the children off at the school.

The driver then headed home by motorcycle.

Teo Jia said: "My son might have fallen asleep at that time, and the driver probably didn't notice him."

Local media reports on Friday, 2nd May, said that the heartbroken father revealed that a teacher called him later that day at around 1 pm, saying that his son was in hospital in critical condition.

He said that when he arrived at the hospital, his son, an only child, was "lying motionless, weak, and not breathing".

Picture shows the five-year-old boy Yu Zie, undated. He was left in a school bus and died in Johor, Malaysia. Note: Image is a screenshot from video. (Newsflash/NX)

He said: "The doctor said they had done everything they could to save him."

He added: "We found out my son had died near the van door — maybe he was trying to get out but couldn't."

Local media reports said that the boy's death has been determined to have been caused by a lack of air.

The school van driver, not named, has been arrested and the police are investigating the incident.

(Joseph Golder/newsX)