'Bike-jacking' of London cyclists on the rise
More than 550 people were mugged for their bicycles in London in the past year, figures released to BBC London show.
The Metropolitan Police, who compiled the data, said gangs have been known to attack cyclists for their bikes, often along quiet routes at night.
The act has become known as "bike-jacking".
More than 10 bicycles were stolen this way each week in the past 12 months - more than in both previous years.
While muggers have traditionally targeted wallets or mobile phones, police say bikes are now seen as a quick way to make money.
Some are worth thousands of pounds and can be sold on easily for significant sums.
Some cyclists say the fear of being mugged is forcing them off quieter routes and onto busy roads, particularly at night.
The charity The Safety Box says bike-jacking is sometimes used by gangs as an initiation for members and this makes young cyclists vulnerable.
It is running lessons at schools across the capital teaching children awareness of the dangers and how to react if targeted.
Cyclist Alex Sweeting chased a group of muggers he saw stealing a bike from another man.
He said: "It is concerning - whether you're locking your bike up, cycling along or waiting at traffic lights, you've always got this fear you could have your bike stolen and all because a bike is a quick sell."
Some campaigners have criticised police for what they call a "poor response" but officers have admitted they are trying to identify particular danger spots.
Ch Insp Mike West said: "We scan every day for crimes of note and if we pick up on any trends or analysis which would lead us to a hot spot area to deal with crime then that's what we'll do.
"We'll match our resources to where the problems are and you'll generally see a increased uniformed presence."