A 92-year-old man was robbed of £500 after he withdrew the money from a bank.
Two men in their late teens or early twenties were loitering in the Portswood Road branch of Barclays Bank between 2.30 and 3pm on Tuesday, August 6.
Police believe the men followed the pensioner from the bank after he took out the £500 in cash.
The man stopped briefly at Sainsbury's and when he reached a car park in Shaftesbury Avenue, he was assaulted and forced to the ground.
The victim suffered a serious hand injury and needed surgery at Southampton General Hospital on Thursday.
We need urgent contact from anyone who was in Barclays Bank, Portswood, or near Sainsbury's between 2.30 and 3pm. We also need to hear from anyone who saw the assault. We need to arrest these robbers before they strike again."