Vic car smash injures five

A woman is in a critical condition in hospital after two cars collided at St Kilda in Melbourne.

Ambulance Victoria's Ray Rowe said the female driver, aged in her early 20s, suffered life threatening upper body injuries in the crash just after 4.30pm (AEDT) on Wednesday.

She was taken to hospital along with her two female passengers who suffered serious injuries.

One of the women was trapped in the vehicle for 45 minutes and had to be released and removed by Melbourne Fire Brigade officers.

A female passenger in her early 20s who was in the other vehicle was also taken to hospital with serious injuries.

The male driver of the vehicle, aged in his early 20s, was not injured and is assisting police with their inquiries.