One woman died and two girls were in serious condition a day after being attacked on a Swiss train by a man armed with a knife and flammable fluid, St Gallen cantonal police said on Sunday.

The 34-year-old woman died from her injuries on Sunday morning, police said. The girls, aged 6 and 17 years old respectively, were in serious condition, as was the suspected assailant injured by the fire he set in the train.

Five people were stabbed or burned during an attack by a 27-year-old Swiss man on the train nearing the Salez station on a trip between Buchs and Sennwald in St Gallen, a canton in the northeast of the Alpine republic.

A sixth suffered smoke inhalation as he came to the aid of the others.

Three victims and the suspect remained in hospital on Sunday morning.

In their criminal investigation, police searched the home of the suspect, who lived in a neighbouring canton, but could not reveal the results of the search.

They said they had found no indication of a politically or terrorist motivated act. "The motive remains unclear," they said in a statement. "There is currently none that can be found."- Reuters