WASHINGTON (REUTERS) - Special Counsel Robert Mueller has collected sufficient evidence to charge Michael Flynn, US President Donald Trump's former national security adviser, and his son, NBC News reported on Sunday, citing multiple sources familiar with the investigation.

NBC News said Mueller's team was looking at possible money-laundering charges, lying to federal agents, and Flynn's role in a possible plan to remove an opponent of the Turkish president from the United States in exchange for millions of dollars.

Mueller is increasing pressure on Flynn following his indictment of former Trump campaign manager Paul Manafort, NBC News said.

Flynn served 24 days as Trump's national security adviser but was fired after it was discovered he had misrepresented his contacts with a Russian diplomat to Vice President Michael Pence.

Peter Carr, a spokesman for Mueller's office, declined to comment. Robert Kelner, Flynn's lawyer, also declined to comment.

Barry Coburn, a lawyer for Michael Flynn Jr., declined to comment, although the younger Flynn appeared to address the report in a tweet. "The SJW are out in full this morning....the disappointment on your faces when I don't go to jail will be worth all your harassment...," the younger Flynn wrote, using an acronym for"social justice warriors," a pejorative often used in reference to liberals.