A man suffered serious injuries after being stabbed in the back during an early hours assault.
The victim and his friend were set upon by a gang of four men outside a Subway sandwich shop after a night out.
Both received stab wounds after being attacked from behind with a knife.
The most seriously injured man suffered a punctured lung.
Police are now examining CCTV footage from the area, in Chapel Road, Worthing, to try and identify the gang.
It is believed they followed the pair along Chapel Road before pouncing, just after 3am on Sunday.
Detective Constable Peter Davis, from Worthing CID, said: "This was an unprovoked assault on two young men returning home from a night out.
"It could have resulted in more serious or even fatal wounds because it involved the use of a knife."
Police are appealing for witnesses to the attack or anyone with information about it to contact them on 0845 6070999.
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