Two teenage girls have been charged after a man was burnt with a cigarette and bashed during an attempted robbery.

Police say the incident started after a 33-year-old man got on a train at Seven Hills in Sydney's west last night.

At a about 10pm, a group of two males and two teenager girls boarded the same train at the next stop, Toongabbie, and allegedly confronted the man.

Officers say the two males held back the man's arms, while one of the girls allegedly burnt his head with a lit cigarette.

Both girls allegedly punched the man in the head repeatedly, and demanded money from him.

The attack continued for three stops later, at Parramatta Railway Station, train guards boarded the carriage and witnessed the attack.

The two females were arrested and taken to Parramatta Police Station where they were charged with attempted aggravated robbery.