A co-founder of the fraudulent OneCoin cryptocurrency has been sentenced to serve 20 years in a US prison.

Sebastian Karl Greenwood colluded with others, including the so-called "Cryptoqueen" who is now on the FBI's top 10 Most Wanted list, officials say.

They are accused of scamming more than $4bn (£3.2bn) from investors.

Greenwood, 46, a citizen of the UK and Sweden, was arrested in Thailand in July 2018. He pleaded guilty to wire fraud and money laundering in December.

Officials say OneCoin, which was founded in 2014 in Bulgaria, functioned as a global pyramid scheme.

Greenwood started and ran the company with Ruja Ignatova, the so-called Cryptoqueen who has not been seen since vanishing in Greece in 2017.

OneCoin sought to benefit from the success of Bitcoin, officials say, and "used the notoriety of Bitcoin to convince investors that OneCoin was the next 'can't miss' investment opportunity".

"In reality, unlike legitimate cryptocurrencies, OneCoin had no actual value and was conceived of by Greenwood and Ignatova as a fraud from day one," prosecutors with the US Attorney's Office for the Southern District of New York said in a news release on Tuesday.

The statement claimed that together, they "operated one of the largest fraud schemes ever perpetrated".

"We hope this lengthy sentence resonates in the financial sector and deters anyone who may be tempted to lie to investors and exploit the cryptocurrency ecosystem through fraud," said US Attorney Damian Williams.

The sentence on Tuesday was handed down by a federal judge in Manhattan. Prosecutors say many OneCoin victims were from the New York region.

The BBC podcast The Missing Cryptoqueen has been documenting the search for Dr Ignatova, the original public face of OneCoin.

The ex-McKinsey consultant had appeared at numerous events and on social media to promote the scheme.

But she disappeared from view around October 2017 and there has not been a confirmed sighting since.

The FBI has offered up to $250,000 for information leading to her arrest, according to the FBI's Most Wanted website.

Her FBI profile says she "is believed to travel with armed guards" and "may have had plastic surgery or otherwise altered her appearance".