Bullies robbed two boys for their mountain bikes at knifepoint in Widnes.
Detectives are investigating after the two "slim" youths struck at Upton Rocks park near the Colvend Way entry at around 2.20pm on Saturday, February 8.
A Cheshire police spokesman said the robbers, one armed with a knife, approached the victims and demanded their bicycles.
The boys, aged 13, handed over their bikes and a small amount of cash.
The muggers rode off along Queensbury Way towards Hough Green.
They are described as white and about 19 years old.
They were slim with facial stubble and Liverpool accents, police said.
One robber was wearing a green Parajumpers jacket with the hood up.
The other was wearing a black bubble jacket and a grey North Face balaclava.
The stolen bicycles are GT mountain bikes - one was dark navy blue and the other was matt black.
Enquiries are ongoing and detectives are keen to hear from anyone in the area who saw anything or anyone who has dashcam or CCTV footage.
Detective Inspector Ian Whiley, of Widnes Local Policing Unit, said: "The victims, both 13-year-old boys, were subjected to a terrifying ordeal that has understandably left them extremely shaken up.
"We are determined to establish the identities of the offenders, bring them to justice and have the stolen mountain bikes returned to their rightful owners.
"Enquiries are ongoing and I urge anyone who was in the area and saw anything that may aid our investigation to come forward.
"The same goes for anyone who thinks they may know who the offenders are or have CCTV or dashcam footage of them.
"We also want to speak to anyone who believes they may have seen the stolen mountain bikes since the robbery took place."
Anyone with information or footage that may help the investigation should call Cheshire Constabulary on 101, quoting IML 631991, provide details via www.cheshire.police.uk or contact Crimestoppers anonymously on 0800 555 111.
