A video has surfaced of a boy claiming that he witnessed a man killing his grandparents at their house in Jalan Tepi Laut, Tanjung Sepat, Banting this morning.

The one minute and 37-second clip shows the 12-year-old boy seated on a bicycle and relating the incident to an unknown person. The house can be seen burning in the background.

The boy, whose three-year-old and nine-year-old siblings also perished in the murder-cum-arson, claimed that a masked robber had attacked his grandparents with a parang.

According to the boy, his father was at work when the incident occurred, while his grandparents, identified as Lim Maik Shak, 68 and Chia Tee Nang, 73, and siblings were asleep.

After slashing his grandparents, who had confronted the robber, the boy said the suspect set the house on fire before fleeing.

The boy claimed he managed to escape as he was hiding in the toilet located at the back of the house and fled the premises when the robbers left.

Meanwhile, NST Online quoted Kuala Langat district police chief Azizan Tukiman as confirming that the boy escaped unhurt but is currently being treated at the Banting Hospital for trauma.

"We will record his statement after he feels better. He is still traumatised by the incident," he said.

The police had classified the case as murder when they found slash and stab wounds on three of the victims.

Police received a distress call regarding the fire about 5.50am.

According to news reports, investigators found traces of accelerants around the fuel tank of the family car, which they believe was used to make the fire big enough to raze the wooden house.