Police are investigating possible links between four robberies carried out on bookmakers in Glasgow and Paisley in the space of a few days.
Two of the robberies took place in the south side of Glasgow, while a third occurred at Hillington.
A possible link has also been established to a fourth raid in Paisley on Friday.
Strathclyde Police said the robberies may have been carried out by the same man.
The first incident took place last Thursday when a man went into a Tote branch in Kelvin Avenue, Hillington, and demanded money from two female members of staff.
Strathclyde Police said he appeared to threaten the women with a firearm, although no weapon was actually used and nobody was injured.
The man made off with a small amount of cash.
On Friday, a similar incident took place at William Hill Bookmakers in Glasgow Road, Paisley.
Two other similar robberies were carried out on Saturday at Ladbrokes Bookmakers in Hillington Road South and William Hill Bookmakers in Main Street, Barrhead.
The suspect is described as white, about 5ft 10ins tall and with a medium build. He was wearing dark-coloured clothing and a black balaclava or ski mask.
Officers are currently studying CCTV and carrying out door-to-door inquiries in an effort to obtain further details about the suspect.
Det Insp Pat Campbell said: "We are following a number of lines of inquiry, however, it would appear that these robberies may have been carried out by the same man.
"Fortunately, no-one was injured in the incidents but the staff have been left extremely frightened and distressed as a result of their ordeal.
"The areas would have been particularly busy with pedestrians and traffic at the time of the robberies and I would therefore like to speak to anyone who was in the area at the time."
He added: "It is possible they may have vital information which could help us trace the man responsible for these crimes."