Bangkok (AFP) – The number of monks killed has risen to 10 after an 11-year-old boy drove a pickup truck into a Buddhist procession in Thailand, officials said Friday.

Ten other people were still hospitalised after Thursday's crash -- two in critical condition and eight with injuries -- according to the latest update from Mukdahan Hospital, in the northeast of the country.

A group of 35 monks and five lay followers were walking along a roadside in Mukdahan province during a pilgrimage when a truck ploughed into them.

Police said it was driven by an 11-year-old who had taken his parents' vehicle without permission.

Five monks died at the scene, and another five died later in hospital.

Prayut Ruanthongkam, chief of Mukdahan City Police, told AFP on Friday the boy was unable to give a statement to police.

He had been referred to child welfare authorities for assessment, accompanied by his mother.

In Thailand, children under the age of 12 have no criminal liability.

Police were also taking witness testimony from surviving monks as part of the investigation, Prayut said.

Buddhist monks are highly venerated in Thailand, entrusted with preserving and passing on the Buddha's teachings.

They often hold public processions and are widely seen receiving alms of goodwill from ordinary Thais.

A representative of Wat Roi Phra Phutthabat Phu Manorom, a hilltop temple in Mukdahan, told AFP the temple had taken in surviving and recovering monks, along with other followers involved in the procession.