A robbery victim suffered serious head injuries when he was attacked in Brighton.
The robbery was one of two which happened at the weekend and which detectives believe may be linked.
Sussex Police said: “Police are appealing for witnesses following two Brighton robberies which are believed to be linked.
“The first of the robberies occurred at the bottom of St James’s Street, Brighton, at around 1am on Sunday (7 April).
“The victim, a man in his thirties, was walking home when he was assault, believed to have been knocked unconscious and had his phone stolen.
“The second robbery occurred nearby in Steine Street at around 3.30am on the same date.
“Two men, one in his thirties and the other in his forties, were assaulted and their phones were also stolen.
“One of the victims suffered serious head injuries and was taken to the Royal Sussex County Hospital.”
Investigating officer Detective Constable Paul Heal said: “These were serious unprovoked attacks on members of the public who had been enjoying a night out.
“We believe the two robberies are linked and are appealing to any member of the public with information to get in contact with us without delay.
“Did you witnesses either of the assaults?
“We are currently not linking these assaults to any other matters.
“You can report information either online or by calling 101 quoting Operation Lacoste.”