CCTV captured two young muggers targeting teenagers as they walked along a street in Bolton.
The footage shows two figures approaching girls from behind before appearing to focus on one of their victims.
They appear to attempt to rip something from around her neck and then flee.
Today (Tuesday) Greater Manchester Police confirmed brief details about the crime shown in the footage, which has been widely shared on social media.
They confirm a necklace was stolen from a 15-year-old girl during the incident, which they are treating as a robbery.
The attack happened on Walnut Street in the Astley Bridge area of Bolton on Sunday.
A statement from Greater Manchester Police said: "Enquiries have established that two teenage girls had been walking along Walnut Street, Bolton when they were approached by two unknown males from behind.
"One of the males then stole a necklace from one girl and both males fled the scene.
"No arrests have been made."
Anyone with information can report online or by using the LiveChat function at www.gmp.police.uk. Alternatively, call 101 quoting log 2873 of 16/05/21 or Crimestoppers anonymously on 0800 555 111.
