Four arrests have been made over two armed raids in Sheffield in the space of 24 hours.
Detectives are quizzing the suspects over robberies at Spar in Bocking Lane, Greenhill, at 9.40pm on Monday and another at McColls in Lowedges Road, Lowedges, the night before
In the first raid, one of two robbers involved threatened staff with a knife before using it to prise the till open.
They escaped with cash and a quantity of cigarettes.
In the Spar raid, two men were involved again and staff were threatened with a knife before the till was forced open.
The men in both incidents wore dark coloured clothing and had their faces covered
Detectives are linking both incidents.
Anyone with information should call South Yorkshire Police on 101.