Pop star Prince is demanding that video sharing website YouTube removes clips of his recent concerts in London.
Prince is nearing the end of a run of 21 sold-out gigs in London
The singer says he is taking action against the site, and others like it, to "reclaim his art on the internet".
More than 1,000 unauthorised clips have been taken down in the last few days, according to Web Sheriff, the UK firm he has hired to enforce the ban.
The star is also targeting online shops which, he says, infringe his copyright by selling unauthorised merchandise.
"Prince believes strongly that... copyrights should be protected across the board," a spokesman for the star said.
Prince has spent the summer playing 21 gigs at the O2 arena in London, which end next week.
Fans have been banned from taking photographs or video footage on their mobile phones, but many have still posted clips on YouTube.
John Giacobbi, managing director of Web Sheriff, said: "Some artists are very relaxed about the use of their image and music on the internet, some less so.
"Prince feels very strongly that people should remember his concerts as they were, not as some grainy mobile phone footage."
The artist has also instructed Web Sheriff to police unauthorised distribution of his music on file-sharing websites such as Pirate Bay, and is seeking to stop auction sites like eBay from selling unauthorised merchandise.
Mr Giacobbi said: "We are not targeting fans who might want to sell their copy of Purple Rain, we are targeting companies in China manufacturing Prince handbags and selling them in their thousands.
YouTube also carries authorised Prince videos
"Prince's actions are a brave and pioneering step to challenge the status quo and hand control over internet rights back to the artists."
Prince has been famously protective of his artistic rights, becoming embroiled in a squabble with record company Warner Brothers over the ownership of his master tapes in the 1990s.
As part of his protest, he changed his name to a symbol and wrote the word "slave" on his cheek during public appearances.
Since fulfilling his contract with the company, he has only released albums online or through special one-off deals with other record labels.
In the UK, his most recent album, Planet Earth, was given away free with the Mail On Sunday newspaper.
Several websites offered copies of the album for download as soon as the paper went on sale - despite the album being sold commercially in the rest of the world.