Attacker on camera.

THIS is the moment a youth sprayed CS gas in the face of two teenage girls in an unprovoked attack on a train.

One of the victims needed hospital treatment after she was overcome by fumes, and because of irritation to her face and eyes.

Police said the attack happened on a train travelling between Richmond and St Margaret's stations in southwest London.

The Metropolitan Police said incidents involving CS gas are increasingly common.

A British Transport Police spokesman said: "This would seem to be a completely random and unprovoked attack."

CAPTION(S):

Camera clue - footage of the attacker