Detectives are appealing for information following the attack which occurred on Friday evening.
At around 11pm a 45-year-old man was found seriously injured after being ejected from a car, described as reddish in colour, in Main Street in Old Bonhill, Alexandria.
Emergency services attended and the victim was taken to the Queen Elizabeth University Hospital where he is receiving treatment for serious facial, hand and leg injuries.
From enquiries carried out so far it is understood that prior to the victim being found on Main Street he was assaulted near to Renton Road, Dumbarton.
Detective Constable Georgia Callander said: “Enquiries are at a very early stage to establish the full circumstances surrounding this serious incident and we are appealing for members of the public to come forward with any information.
“If you were near to Main Street, Old Bonhill, or Renton Road, Dumbarton, on Friday night and saw or heard anything suspicious it is important that we speak to you.
“We would also urge anyone with private CCTV or dash-cam footage of the area to check in case they may have captured something which could be of significance to our investigation.
“Anyone with information is asked to contact Police Scotland on 101, quoting incident number 4840 of Friday, 31 May, 2024. Alternatively you can call Crimestoppers anonymously on 0800 555 111.”
