A train passenger was injured when she was allegedly set upon by a gang of seven teenagers in a violent early morning attack.

Police said the 23-year-old Clayton woman was approached by a 19-year-old man and six girls, aged between 16 and 15, on a south-bound Pakenham train about 5am on March.

A woman was allegedly assaulted on a Melbourne train.

A verbal altercation took place, leading to the alleged assault. The woman dropped her purse, and the man allegedly picked it up and stole it.

The woman was taken to hospital with non-life threatening injuries.