A mental patient allegedly, and inexplicably, burned down 10 hectares of forest in the central province of Quang Ngai on Thursday.

Local residents stopped the fire, but not until after it had engulfed large swathes of land.

The fire started at around noon in the mountainous Tay Tra District and burnt for five hours, destroying many iron wood trees two to three years old.

More than 100 local residents had helped fire fighters and authorities extinguish the fire.

Each of the residents was awarded VND1 million (US$53).

Investigators found that Ho Van De, who is being treated for mental and physical problems at a local medical station, had started the fire.

De had burnt more than one hectare of forest a month ago, more than a kilometer from the new spot.

Some young men who lost trees to the fire beat him and broke his legs after the latest incident.