A woman was filmed being punched, kicked and stomped-on after a mass brawl broke out at a central Melbourne station.

Up to 40 youths have been caught on camera brawling outside Flinders Street Station about 4.30am.

Mobile phone footage shows the fight spilling to a nearby tram stop where a girl is singled out by a group with witnesses saying she was pushed to the ground and repeatedly kicked and punched in the head.

Mobile phone footage showed the violent brawl outside Flinders Street Station. (9news)

A group of women singled out another women kicking and punching her in the head. (9news)

“They took her over the road to a tram stop in the middle of the road, once she was on the ground there was a group of four just stomping on her”, Ryan Baily told 9News.

The brawl was over in less than a minute when police arrived causing the group to scatter.

Earlier in the night a man was arrested for assaulting a PSO with other PSO’s being required to use capsicum spray to diffuse the situation.

Officers say they were surrounded by a large group of aggressive young men.

The assault happened after a man assaulted a PSO earlier in the night. (9news)