Media playback is unsupported on your device Media caption The National Crime Agency released this video to show how easy it is to be caught out by blackmailers

The suicides of four British men in the last year have been linked to so-called "sextortion", police say.

The number of people reporting webcam blackmails has more than doubled from 385 in 2015 to 864 up to November 2016.

The National Crime Agency (NCA) said it believed it was also significantly under-reported and actual numbers of victims were likely much higher.

The National Police Chiefs' Council (NPCC) said the rise in cases was "worrying".

"Sextortion" is a form of blackmail where criminals use fake identities to befriend victims online before persuading them to perform sexual acts in front of their webcam.

The images are recorded by the criminals who then threaten to share them with the victims' friends and family unless they give in to their demands for payment.

Image copyright Mid Ulster Mail Image caption Schoolboy Ronan Hughes, 17, took his own life after being blackmailed online

About 95% of victims of sextortion were men or boys, figures released by the NCA showed.

It said victims were aged between 14 and 82, with the highest proportion being men aged between 21 and 30, and with a substantial proportion in the 11-20 age group.

In October, a 31-year-old man was charged by police investigating the suicide of schoolboy Ronan Hughes.

One of the four men who took their own lives, 17-year-old Ronan killed himself in June 2015 after being tricked into posting images on a social networking site.

Roy Sinclair from the NCA said there was still "huge under-reporting of these kinds of offences".

"This is often because victims feel ashamed or embarrassed, but of course criminals are relying on that reaction in order to succeed," he said.

'I thought about suicide'

Image copyright Thinkstock

Teenager Gary, from Hampshire, was blackmailed after he started visiting dating websites and was asked to talk over webcam.

"She invited me onto webcam, where she looked similar to her profile picture... the video call lasted for around 30 to 45 minutes, all on the phone. She said 'show me a bit more, and show me your face'.

"Then the messages came up, saying 'pay £500 or this is going all over social media. I want £500', and listing my friends' details."

Gary said he worried what would happen if the video went on social media, fearing he may lose his job.

"I thought about suicide, it would have been too embarrassing, I would not have been able to face anyone."

Instead of going to the bank, Gary said he went to the police, who "handled it well" and helped him to "talk to someone".

"Since then I've tried to put it to the back of my mind, and I've moved on with my life. There is always life afterwards, but I would not be here today if I had not spoken to anyone."

Assistant Commissioner Martin Hewitt, the NPCC's lead for kidnap, extortion and adult sexual offences, said it was a "very damaging and invidious crime".

"The really key point is that as a result of this criminality, we have had four young men in the UK who have killed themselves - taken their own lives - because they saw no way out of a situation that they had gotten into.

"This is organised crime. Whilst the individual cases themselves may involve relatively limited amounts of money, this is being organised by well-equipped, often off-shore organised crime groups that are facilitating this activity."

Last year more than 40 arrests were made in the Philippines in relation to sextortion and there is one ongoing international prosecution connected to one of the suicides reported this year.

Mr Hewitt said the NPCC was providing information to police forces to better equip them to deal with these crimes when they are reported as well as a public awareness campaign to make potential victims, and all those around them more knowledgeable about what to do.

'She sent me photos of my family'

Jimmy, in his 20s, from Northern Ireland, met a woman on an online dating app and eventually exchanged photos, including sexual images.

"Literally 10 minutes after I'd sent her my profile I got a message saying, 'What would you do if I sent these photos to your friends and family?'

Jimmy said the woman then told him to subscribe to live webcam websites and then demanded money by wire transfer, messaging him "every few minutes to check where I was".

"She started sending me photos of my family from my social media contacts, saying she would send the pictures to them.

"It was really stressful and I didn't know what to do. I caved in and sent her £150. She said she wanted £300 but I said no, deactivated my social media account and went to the police."

"I was so worried about what my friends and family would think. I've spoken to my mum about it, that was tough enough, but I still can't talk to anyone else."

What to do if you have been targeted:

Don't panic - the police say they will take your case seriously, and will not judge

Don't pay - many people who have paid continue to get more demands for money, and sometimes the offenders will still post the videos

Don't communicate any more with the criminals - take screen shots of all messages, temporarily suspend your social media accounts so the evidence is kept, and report the incident to any social media service you use

Preserve evidence - make a note of any details provided by the offenders and don't delete any correspondence

Source: NCA website