Filesonic has disabled its sharing functions, allowing users to access only their own files.

Uploaded.to has blocked US access to its site entirely, with a message saying "sorry about that".

Experts said that the sites were attempting to show that they were taking piracy seriously.

"If those websites are found to be communicating the works - ie facilitating sharing - then that's the key risk in terms of criminal liability," said Adam Rendle, a copyright lawyer from London-based law firm Taylor Wessing.

Filesonic, which is based in the UK and Hong Kong, has not released a statement about its move to block sharing.

However, customers visiting the website were greeted with a message stating simply: "All sharing functionality of Filesonic is now disabled. Our service can only be used to upload and retrieve files that you have uploaded personally."

Read more: http://www.bbc.co.uk/news/technology-16679174