Footscray Police are warning people to watch out for thieves snatching mobile phones.

Unsuspecting victims are being asked the time by a stranger and when the person checks the time on their mobile phone, it is being snatched from their hand.

Police say this has occurred to some pedestrians and public transport commuters.

In another incident a woman listed an iPhone 6 for sale through an online advertising platform.

Police say a man expressed interest in the phone and arranged to meet up with the woman on June 12 on Saltriver Place.

The man told the woman he wanted to check if the phone was compatible with his sim card, which was inside a nearby car.

She walked with the man a short distance before he snatched the phone from her, knocked other items out of her hand and then fled on foot.

Police have released images and CCTV footage of a man they believe may be able to assist with their enquiries.

The man is perceived to be of African appearance and aged about 20 to 25 years old.

He was wearing grey tracksuit shorts, a grey Michael Jordan beanie, red shoes and a white T-shirt, and was last seen running south along the Maribyrnong River.

Anyone with information is urged to contact Crime Stoppers on 1800 333 00 or submit a confidential crime report at www.crimestoppersvic.com.au