Megaupload founder Kim Dotcom has offered a $5 million reward on Monday to whistleblowers for information to help fight an online piracy case brought against him by the United States, Agence France-Presse reported.

The German national had his website shut down in January 2012 and has long claimed that U.S. authorities, aided by close ally Wellington, illegally targeted him on behalf of Hollywood studios in one of the largest copyright infringement cases ever brought.

Dotcom, who is resisting extradition from New Zealand, said he had to resort to offering the "bounty" since all the odds were stacked against him, Sky News reported.

"My case is unfair," the Internet mogul tweeted. "I was declined discovery, I didn't get my own data back, I need whistleblowers I am offering USD $5M."

The multi-million dollar offer was aimed at helping Dotcom prove that allegation, with any whistleblower provided free legal representation by him, he told tech news website TorrentFreak.com.

"We are asking for information that proves unlawful or corrupt conduct by the US government, the New Zealand government, spy agencies, law enforcement and Hollywood," he said.

"It is the opinion of my legal team that disclosure of such information would be lawful. I would also guarantee any whistleblower coming forward would have the best legal representation at zero cost."

Although Dotcom's extradition hearing has already been delayed several times amid legal wrangling over evidence disclosure, it is scheduled to begin in Auckland on July 7, according to AFP.

Charges of racketeering, money laundering and copyright theft and a potential jail term of 20 years will be faced by Dotcom and his three co-accused if they are sent to the United States.

Megaupload made more than $175 million in criminal proceeds, the U.S. justice department said.

Lawsuits have also been filed by major music labels and film industry in the U.S. against the file-sharing website.

Dotcom, 40, has launched a new venture called Mega while on bail.