Former US national security adviser Michael Flynn pleaded guilty on Friday to lying to the FBI about his contacts with Russia, and he agreed to cooperate with prosecutors delving into the actions of President Donald Trump's inner circle before he took office.
The dramatic turn of events also raised new questions about whether Trump's son-in-law, Jared Kushner, had a role in those Russia contacts.
Flynn was the first member of Trump's administration to plead guilty to a crime uncovered by special counsel Robert Mueller's wide-ranging investigation into Russian attempts to influence the 2016 US election and potential collusion by Trump aides.
Under a plea bargain deal, Flynn admitted in a Washington court that he lied when asked by FBI investigators about his conversations last December with Russia's then-ambassador, Sergei Kislyak, just weeks before Trump took office.
Prosecutors said the two men discussed US sanctions against Russia and that Flynn also asked Kislyak to help delay a UN vote seen as damaging to Israel. On both occasions, he appeared to be undermining the policies of outgoing President Barack Obama.
They also said a 'very senior member' of Trump's transition team had told Flynn to contact Russia and other foreign governments to try to influence them ahead of the UN vote.
Sources told Reuters that the 'very senior' official was Kushner, a key member of Trump's transition team and now the president's senior adviser.
Kushner's lawyer, Abbe Lowell, did not respond to multiple requests for comment. He has previously said Kushner has voluntarily cooperated with all relevant inquiries and would continue to do so.
Flynn's decision to cooperate with Mueller's team marked a major escalation in a probe that has dogged the president since he took office in January.
There was nothing in the court hearing that pointed to any evidence against Trump, and the White House said Flynn's guilty plea implicated him alone.
'Nothing about the guilty plea or the charge implicates anyone other than Mr. Flynn,' said Ty Cobb, a White House attorney.
Flynn, a retired army lieutenant general, only served as Trump's national security adviser for 24 days. He was forced to resign after he was found to have misled Vice President Mike Pence about his discussions with Kislyak.
But Flynn had been an enthusiastic supporter of Trump's election campaign and the president continued to praise him even after he left the administration, saying Flynn had been treated 'very, very unfairly' by the news media.
A small group of protesters yelled 'Lock him up!' as Flynn left the courthouse on Friday, echoing the 'Lock her up!' chant that Flynn himself led against Trump's Democratic rival, Hillary Clinton, in vitriolic appearances on the campaign trail.