A baby has been left on the side of a rural highway after a mother was allegedly carjacked when she pulled over to help a man.

Police believe the 51-year-old man flagged down the woman on the Murray Valley Highway on the outskirts of Swan Hill on the Victoria-NSW border about 11.10am on Wednesday.

The 36-year-old woman got out of her car to help the man. However, police allege a struggle broke out before the man stole the Holden Commodore with a baby inside.

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The seven-month-old baby was found by a passerby on the side of the highway a short distance away.

The woman, who suffered minor injuries, and her uninjured baby were quickly reunited and taken to hospital.

Police said the car was found abandoned in bushland about 12km away.

The 51-year-old Swan Hill man was arrested several hours later and has since been charged with several offences including carjacking, committing an indictable offence whilst on bail and contravening condition of bail.

He is also facing child stealing and unlawful assault charges.

The man has been remanded to appear at Mildura Magistrates’ Court on December 2.