Almost 900 people reported they have been victims of webcam blackmail this year in the UK. Flickr/David Burillo

At least four male suicides in the UK have been linked to "webcam blackmail" — a form of extortion where victims are tricked into performing sex acts — the UK's National Crime Agency (NCA) and National Police Chiefs Council (NPCC) have reported.

Criminals use the identity of attractive women (who may have been coerced into these actions themselves) to befriend victims online, persuade them to perform sexual acts in front of their webcam, record them, and then threaten to share images with their friends and family, the NCA explains.

Victims of this so-called "sextortion" have more than doubled from 385 to 864 in the past year, and that's just those who have reported the crime.

Roy Sinclair, from the NCA’s Anti-Kidnap and Extortion Unit (AKEU), said: “There is huge under-reporting of these kinds of offences, often because victims feel ashamed or embarrassed, but of course criminals are relying on that reaction in order to succeed."

The highest proportion of victims are men aged between 21 and 30, but there were also a number of victims in the 11-20 age group, the NCA reported.

Schoolboy Ronan Hughes, who killed himself at the age of 17, was one of the four suicides linked to the crime, the BBC reports. In October, a 31-year-old man was charged by police investigating Hughes' death, the BBC reported. The man was charged with producing and distributing indecent images of children and blackmail.

Organised crime groups "largely based overseas in countries including the Philippines, Ivory Coast and Morocco, are behind a large proportion of sextortion attempts," according to evidence from the Police and the NCA.

The NCA has launched a new public awareness campaign to give advice to those who have been, or are likely to be, targeted.

The NPCC's lead for kidnap, extortion, and adult sexual offences Martin Hewitt said: “Our message to those who are targeted: don’t pay and don’t panic – call us for help. Your safety and welfare will be at the heart of our investigations."

The NCA's Advice for victims:

"DON’T PANIC - The police will take your case seriously, will deal with it in confidence and will not judge you for being in this situation. You are not alone.

DON’T PAY - Many victims who have paid have continued to get more demands for higher amounts of money. In some cases, even when the demands have been met the offenders will still go on to post the videos. If you have already paid, check to see if the money has been collected. If it has, and if you are able, then make a note of where it was collected from. If it hasn't, cancel the payment.

DON’T COMMUNICATE further with the criminals. Take screen shots of all your communication. Suspend your Facebook account (but don’t delete it) and use the online reporting process to report the matter to Skype, YouTube etc. to have any video blocked and to set up an alert in case the video resurfaces. Deactivating the Facebook account temporarily rather than shutting it down will mean data is preserved and will help police to collect evidence."

Watch the NCA's video message: