The investigation into the Trump campaign's alleged ties to Russia has taken a turn.

President Donald Trump's former national security adviser, retired Lt. Gen. Michael Flynn, has offered to be interviewed about the Trump campaign's ties to Russia, his lawyer said on Thursday.

The catch? He wants immunity from "unfair prosecution," his lawyer said.

Flynn made the offer to the FBI as well as the House and Senate intelligence committees through his lawyer.

"General Flynn certainly has a story to tell, and he very much wants to tell it, should the circumstances permit," Flynn's attorney, Robert Kelner, said in an emailed statement, adding that no further comment would be provided on the details of their discussions with the House and Senate intelligence panels.

The FBI and congressional officials are investigating whether there was any collusion between Trump's campaign and Russia during the 2016 U.S. presidential election.

Trump tweeted Friday morning that he supports Flynn's request for immunity. 

"Mike Flynn should ask for immunity in that this is a witch hunt (excuse for big election loss), by media & Dems, of historic proportion!" he wrote.

The president has repeatedly said that his aides do not have any ties to Russia, despite unanswered questions about their contacts with Russian officials during the presidential campaign.

Flynn resigned from the Trump administration in mid-February, after he failed to disclose conversations he had with Russia's ambassador about U.S.-imposed sanctions before Trump took office and then allegedly misled Vice President Mike Pence about those discussions.

With Reuters