Swiss officials say they suspect a bus fire that killed at least six people and injured five in western Switzerland was started deliberately, but was unlikely to be a terrorist act.

The incident took place on Tuesday night in the town of Kerzers - known in French as Chiètres - in Fribourg canton, about 20km (12 miles) from the capital, Bern.

Officials said on Wednesday that a survivor told them a Swiss man in his 60s had sprayed a flammable liquid on his body before setting himself on fire. He is thought to be among the dead.

Fribourg's general prosecutor said the man appeared to be "psychologically unstable", adding: "There is absolutely no evidence to suggest that this was a terrorist act."

According to police, initial findings suggest the man boarded the bus in the Düdingen municipality, 17km south of Kerzers, at around 17:45 local time (18:45 GMT) before setting himself on fire roughly 40 minutes later.

Video posted by local media shows a bus in flames, and a local resident described seeing a thick column of smoke.

Of the five people injured in the fire, police said three had to be taken to hospital and two were still there.

Cantonal police commander Philippe Allain said it was not known where the fire started but that it appeared the doors of the bus had been open. It is not known why passengers did not get out of the vehicle.

Investigators have also been checking the fuel-powered bus to rule out any potential technical cause.

Allain said the victims had not been identified yet, but that they were all born between 1961 and 2009.

In a post on X, Swiss President Guy Parmelin said: "It shocks and saddens me that people have once again lost their lives in a serious fire in Switzerland".

Forty-one people were killed in a deadly fire that broke out in a Swiss ski resort on New Year's Eve.