On Tuesday police released surveillance camera photos of two men sought for questioning over the heist as well as images of some of the rings, bracelets, necklaces and watches taken from Graff Jewellers on central London's New Bond Street. A total of 43 items were taken, with a value of about £40 million, or about $65 million, Scotland Yard said.

The heist occurred Thursday, when two men walked into the jewelry store at about 4:40 p.m. and threatened employees with handguns. As the robbers were leaving the store, they brought a female worker outside with them before leaving in a blue BMW, Scotland Yard said. A shot was fired outside the store, but no one was injured.

The men abandoned the BMW nearby, firing a second shot into the ground, Scotland Yard said. Police believe they switched to a silver Mercedes, then later to a black vehicle, possibly a Ford or Volkswagen.

"This was a well-planned robbery with a number of vehicles used to help the robbers escape," Detective Chief Inspector Pam Mace said in the statement. "These men are extremely dangerous and fired at least two shots in busy London streets as they made their getaway.

"Someone knows who these men are," she said. "They would undoubtedly have spoken about (the robbery) before or boasted about it afterwards. I would urge anyone who recognizes them, knows the whereabouts of the jewelry or has any other information to contact us."

The images show the two men dressed in suits and ties. One man is white, about 30, police said. The second is a black man believed to be in his 30s with short hair. Both men are thought to have spoken with London accents, Scotland Yard said.

The robbery is the latest in a spate of daytime thefts at jewelry stores and designer shops in London's exclusive shopping areas of Bond Street, which includes New Bond Street.

Groups of men or teenagers typically stage "smash and grab" robberies, in which they break the windows and steal anything they can get their hands on before speeding away in waiting cars or motorbikes.

A CNN camera crew filming in March on Oxford Street, near Bond Street, caught a group of thieves speeding away on motorbikes from a jewelry store they had just robbed.