A woman had her mobile phone stolen and another was pushed over while walking through the church yard of St Giles Church in Northampton town centre.
The incident happened at about 9.15pm on Sunday, 28 February.
Officers have released a CCTV image of a man they believe may have information about the robbery. He is described as male, about 5ft 8in, with scruffy dark hair and wearing a bright red jacket.
There were a number of people in the area at the time and anyone who witnessed the incident, or anyone with information about it, can call Northamptonshire Police on 101.
Alternatively, they can call independent charity Crimestoppers anonymously on 0800 555111.