The founder of the outlawed Megaupload file-sharing site denounced on Thursday "the largest data massacre in the history of the internet", after a European firm wiped out private photos, videos and documents stored on servers used by the site.

Dutch firm LeaseWeb said it had in February erased 630 servers rented by Megaupload, about a year after U.S. authorities closed the site and charged its operators with facilitating online piracy, racketeering and money laundering.

"Our lawyers have repeatedly asked LeaseWeb not to delete Megaupload servers while court proceedings are pending in the U.S.," Kim Dotcom said on Twitter.

"We were never warned about the deletion," Dotcom said, adding that the loss of the files had reduced him to tears.

Dotcom, who also goes by the name Kim Schmitz, has New Zealand residency. He and his colleagues are fighting extradition to the United States.

He argues that Megaupload was merely a storage facility for online files, and should not be held accountable for the content of those files.

LeaseWeb said it had been maintaining the servers at its own expense since Megaupload was shuttered in January 2012. After the servers sat inactive for a year, and with no requests to access them, it said it had informed Megaupload that it would delete them.

"After a year of nobody showing any interest in the servers and data we considered our options ... we commenced the re-provisioning of the servers in February 2013," LeaseWeb said in a blog post.