A 31-year-old man arrested in Derry on suspicion of robbery remains in police custody.
Police received a number of reports of attempted robberies at shops in the Waterloo Street, William Street and Strand Road areas of the city on Saturday.
During each of the incidents, which took place between 3.10pm and 3.40pm, a man entered each of the premises and threatened staff with a large knife.
During the attempted robbery at Waterloo Street, the man demanded cash, while at William Street, he asked for cigarettes.
The suspect, who left empty-handed from each premises, was wearing an orange hooded top, with the hood up and pulled around his face and blue jeans. He was also carrying a white cloth shopping bag.
Officers on patrol on Foyle Street subsequently arrested a 31-year-old man on suspicion of robbery with the assistance of members of the public.
Detective Sergeant Richard Donnell said: "These incidents were frightening for the staff.
"They were in their workplace, simply doing their job, and have been left shaken. Thankfully, no injuries were reported. I also want to thank the members of the public for their assistance".
