An 11-year-old drove his parents' pickup truck into a Buddhist procession in Thailand on Thursday, killing eight monks and injuring 10 others, police said.

The group of 35 monks and five lay followers were walking along a roadside in the northeastern Mukdahan province during a pilgrimage when the incident occurred.

"The suspect is a child. The vehicle has been taken for forensic examination to determine the cause," Police Major General Pairoj Thaiphutsa, commander of the Mukdahan Provincial Police, told reporters.

"We've asked the child's parents to come in so we can determine who is responsible for the child's care, so we can go on with legal process," he added.

Police said the boy had taken his parents' pickup truck without permission before losing control of the vehicle and crashing into the monks. Local police also said the boy is now in custody.

The police added the cause of the accident is still under investigation, but said they were told by the monks that they saw the vehicle losing balance before it slid off the road and crashed into the group.

Five monks died at the scene and three more later died in hospital, while more than 10 others are being treated.

Medical and rescue teams deployed

Prayut Ruanthongkam, chief of Mukdahan City Police, told AFP by telephone that the child was a boy aged 11.

Emergency medical and rescue teams were deployed to the scene and the injured were taken to Mukdahan Hospital.

Mukdahan provincial governor Worayan Bunnarat said the case should serve as a wider warning on road safety.

"We've been very strict on road safety in recent years. This case should be a lesson not just for our province, but for the public in general when it comes to preventing road accidents," he said.

"I think everyone involved, especially parents, needs to help, because no one wants something like this to happen."