Donald Trump's former presidential campaign manager, Paul Manafort, has been charged with conspiring to defraud the US in his dealings with Ukraine.
The 12 charges brought against Mr Manafort and one of his business associates, Rick Gates, include conspiracy to launder money.
The charges are the first to stem from an inquiry into alleged Russian meddling in the US 2016 election.
Mr Manafort and his lawyer have arrived at an FBI office in Washington.
An investigation headed by special counsel Robert Mueller is looking into any links between Russia and the Trump campaign.
The indictment against the two men looks at their links to pro-Russian politicians in Ukraine between 2006 and 2015.
According to the indictment, Mr Manafort and Mr Gates acted as "unregistered agents" of Ukrainian politician Viktor Yanukovych and his party, both in opposition and government.
Good news for Trump... for now
By Anthony Zurcher, BBC News, Washington
And so it begins.
For years Paul Manafort operated on the fringes of power, a once-influential Washington player who worked with some less-than-savoury international characters because his services were no longer in high demand domestically.
Then, like many other politicos in Donald Trump's orbit, he was thrust into the spotlight because more established hands wanted nothing to do with the upstart's presidential campaign.
Mr Manafort got his big break but it may end up breaking him. That resulting spotlight has drawn attention to Mr Manafort's past dealings and raised questions about his actions while in at the top of the Trump campaign.
The good news for Mr Trump is these charges stem from Mr Manafort's past business dealings, not his campaign efforts. He is being accused of working for years for pro-Russian Ukrainian politicians and laundering millions in subsequent payments.
It certainly makes Mr Trump's decision to cut Mr Manafort loose last August after details emerged of his Ukrainian ties seem a wise one.
The good news has its limits, however. Mr Manafort will be under growing pressure to co-operate with the Mueller investigation. If he offers up useful information about his time during the campaign, this could be just the first domino to fall.
Mr Yanukovych was deposed as president in 2014 amid mass unrest over his pro-Russian policies.
The team led by Mr Mueller is known to have conducted extensive interviews with several current and former White House officials as part of the inquiry.
Mr Gates has been ordered to surrender to authorities, according to US media reports.
Mr Manafort, 68, has worked on several Republican presidential campaigns, beginning with Gerald Ford's in 1976.
He resigned as chairman of the Trump campaign in August 2016 after being accused over his dealings with pro-Russian politicians in Ukraine. He denies any wrongdoing.
US intelligence agencies have already concluded that the Russian government sought to help Mr Trump win the election.
But President Trump has strenuously rejected allegations of collusion, calling the investigation a "witch hunt".
Have your say
More World Headlines
- At least 42 killed in Zimbabwe bus fire
- Symbolic funeral services for murdered Jamal Khashoggi
- US to cut Africom troops amid focus on Russia and China
- Trump ordered to restore CNN reporter Jim Acosta's access
- Trump attacks Mueller's Russia inquiry as 'absolutely nuts'
- Carmakers lure ride-hailer, delivery drivers in Africa
- White House aide Mira Ricardel removed after Melania Trump row
- Nigeria: Biafra secessionist leader 'must appear in court'
- Lion Air crash: Victim's fiancée takes wedding photos alone
- UK closer to delivering Brexit - May
- UN lifts nine-year Eritrea sanctions
- South Africa minister resigns weeks after sex video scandal
- Brexit: Theresa May to face cabinet showdown over deal
- Trump finally appoints new ambassador to Saudi Arabia
- Over 300,000 Congolese refugees forced to leave Angola