The FBI is warning of an "explosion" in cases of teenagers and young boys being tricked into sending explicit pictures online.

It said there had been a sharp rise in the blackmail scheme which it linked to at least a dozen suicides in the US this year.

The FBI said there had been more than 7,000 reports of sextortion in 2022.

"This is a level of harassment we haven't seen recently," a senior official warned.

In a news release on Monday, the FBI said many of the schemes originated outside of the US in West African countries such as Nigeria and the Ivory Coast.

It cautioned parents to be alert over the holiday period and to make their children aware of the schemes.

"The FBI has seen a horrific increase in reports of financial sextortion schemes targeting minor boys - and the fact is that the many victims who are afraid to come forward are not even included in those numbers," FBI Director Christopher Wray said.

"Victims may feel like there is no way out - it is up to all of us to reassure them that they are not in trouble, there is hope, and they are not alone," he added.

The scam typically consists of someone posing as a woman on social media and luring people into sending explicit images of themselves. The scammer then threatens to make the images public unless the victim sends money.

Children are being targeted in their homes using gaming devices and other apps, officials said, adding that scammers often encourage victims to move to a secondary messaging platform after making initial contact.

Boys between the age of 14 and 17 are generally targeted but children as young as 10 have been interviewed by the FBI.

While the crime is estimated to have garnered millions of dollars in total, an individual scam usually results in a victim sending amounts in the thousands.

"This is a growing crisis and we've seen sextortion completely devastate children and families," Michelle DeLaune, CEO of the National Center for Missing and Exploited Children, said.

"The best defence against this crime is to talk to your children about what to do if they're targeted online," she added.

If a child is being exploited online, contact your local FBI field office or report it online at tips.fbi.gov.

The National Center for Missing and Exploited Children (NCMEC) has outlined steps parents and young people can take if they or their child are a victim of sextortion.

In the UK, help and support is available via the BBC Action Line.