A man has been transported to hospital with "life-threatening" injuries after being shot at Narre Warren South.

A Victoria Police spokesperson said the exact circumstances of the shooting were still being determined.

"Investigators have been told a man was shot in the upper body while seated in a car on Shrives Road about 5:00am," the spokesperson said.

"The man was transported to hospital with life-threatening injuries."

An Ambulance Victoria spokesperson said the man was believed to be in his 20s.

"He was taken to the Alfred Hospital in a critical condition," the spokesperson said.

Shrives Road was closed to traffic with diversions via Centre Road.

Police have asked that anyone who witnessed the incident or can provide any information to contact Crime Stoppers on 1800 333 000 or make a confidential report at www.crimestoppersvic.com.au.