Police are linking two violent robberies at jewellery shops in London's West End.
A staff member was assaulted at Boodle & Dunthorne on Regent Street on 14 October when the store was raided by four men armed with hammers.
Then on 22 October, the Lucie Campbell shop on New Bond Street was targeted by two men. Again a member of staff was attacked.
In both thefts displays were smashed and a number of jewellery items stolen.
Both the assaulted staff are said to be recovering. The worker at Boodle & Dunthorne was treated for multiple head injuries.
Det Insp Andy Dunn, from the Flying Squad, said: "During both these robberies, staff members have been attacked and injured.
"It is important that this gang is caught before anyone else is hurt."
The four suspects are all aged between 25 and 30 years. One is said to be of Mediterranean appearance and stocky build and two are described as black.
The fourth is said to be white, tall and of stocky build.