At least 37 people, including 23 children, have been killed by a former policeman in the deadliest rampage in Thailand’s history.

Armed with a shotgun, pistol and knife, Panya Khamrab opened fire at a childcare centre in north-eastern Nong Bua Lam Phu province.

It’s understood the gunman fatally shot four staff members outside the nursery before he barged through a locked door and began attacking the children inside.

Khamrab killed his wife and child at home after the attack and then committed suicide, police said.

The 34-year-old was suspended from the police in January and sacked in June for drug use.

National Police Chief Damrongsak Kittiprapat said the pistol used in the rampage had been purchased legally and was a privately-owned weapon, not police property.

Image: Lauren DeCicca/Getty Images