Police said the victim was tripped from behind, with the offenders running off towards Felixstowe Road.
The incident happened around 1.45am on Sunday.
A Suffolk Constabulary spokesman said: “A man was walking along the road when he was tripped from behind and then assaulted, causing him to fall to the floor.
“A white and gold iPhone 6 plus was stolen and the two male offenders ran off towards Felixstowe Road.
“The victim sustained a cut to his hand and reddening to his head and face as a result.
“There is no further descriptions of the offenders.”
Officers are urging witnesses or anyone with information about the incident to come forward. Call police on 101 or Crimestoppers anonymously on 0800 555111.
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