A burka-clad knifeman has struck a third travel agent in less than a year, police said today.
Disguised in black Muslim clothing with only his eyes visible, the culprit robbed Thomson Travel in Dunstable, Bedfordshire, on Saturday after threatening two female members of staff.
The raider forced a member of staff to fill his bag with a large amount of money from an office and till before making his escape through the front entrance.
The incident follows two similar robberies in the area last summer.
First Choice travel agent in Dunstable was targeted by a burka-wearing robber on July 7 and the same happened in Thomson Travel in Luton on August 16, Bedfordshire Police said.
Detectives said they were keeping an open mind about whether the three incidents were linked.
A police spokeswoman said: "The pattern the offenders have followed is strikingly similar.
"They walk in, dressed in a burka, approach members of staff quite calmly by knifepoint.
"They leave the shop very calmly and walk off."
The difference is that the Dunstable robber last year was shorter, bigger built and walked differently to the one caught on CCTV in Luton. she added.
Police are appealing for witnesses to Saturday's robbery.
DC Gill Cowley, investigating, said: "This was an extremely frightening incident for the staff and customer in the shop.
"However, they did exactly the right thing by remaining calm and not provoking the offender.
"His disguise was so distinctive we are hoping someone recalls seeing him or even knows who he is."
The man, believed to be of mixed race, was carrying a square black bag with a long shoulder strap and wearing black plimsolls,
The burka is described as black with a silver or grey floral design pattern on one half of the garment.