A group of NFT collectors has paid $4 million to purchase the only copy of a one-of-a-kind album by the rap group Wu-Tang Clan.

A non-fungible token (NFT) is a digital object -- a drawing, animation, piece of music, photo, or video -- with a certificate of authenticity created by blockchain technology.

The album was previously owned by Martin Shkreli, a disgraced executive sentenced to prison for fraud, and sold at auction in July as part of a deal to settle his debt to the US government.

The buyer was kept secret until this week, when PleasrDAO, a group of New York NFT collectors, announced it had purchased the only copy of "Once Upon a Time in Shaolin".

The Wu-Tang Clan's 'Once Upon a Time in Shaolin' album The Wu-Tang Clan's 'Once Upon a Time in Shaolin' album Photo: AFP / Handout

According to US media reports earlier this week, retweeted by PleasrDAO's Twitter account, the group paid $4 million for the two-disc, 31-track album.

They are known among NFT collectors for having acquired digital works by US whistleblower Edward Snowden and the Russian dissident feminist punk band Pussy Riot.

They now hope to share "Once Upon a Time in Shaolin" with the public.

"Although we are bound by the legal agreement underpinning this work of art and may not be able to duplicate and share the music digitally," PleasrDAO said on its website, "we firmly believe there are ways to share this musical masterpiece with the world."