The Russian lawyer who met Donald Trump Jr after his father won the Republican nomination for the 2016 US presidential election counted Russia's FSB security service among her clients for years, Russian court documents seen by Reuters show.
The documents show the lawyer, Natalia Veselnitskaya, successfully represented the FSB's interests in a legal wrangle over ownership of an upscale property in northwest Moscow between 2005 and 2013.
The FSB, successor to the Soviet-era KGB service, was headed by Vladimir Putin before he became Russian president.
There is no suggestion that Ms Veselnitskaya is an employee of the Russian government or intelligence services and she has denied having anything to do with the Kremlin.
The Obama administration last year sanctioned the FSB for what it said was its role in hacking the election, something Russia flatly denies, and Charles Grassley, Republican chairman of the Senate Judiciary Committee, has raised concerns about why Ms Veselnitskaya was allowed into the US at all.
Ms Veselnitskaya did not reply to emailed Reuters questions about her work for the FSB but she later posted a link to it on her Facebook page on Friday.
"Is it all your proof? You disappointed me," she wrote in a post.
"Dig in court databases again! You'll be surprised to find among my clients Russian businessmen... as well as citizens and companies that had to defend themselves from accusations from the state."
Ms Veselnitskaya said she also had US citizens as clients.
The FSB did not respond to a request for comment.
Reuters could not find a record of when and by whom the lawsuit - which dates to at least 2003 - was first lodged but appeal documents show Rosimushchestvo, Russia's federal government property agency, was involved.
It did not immediately respond to a request for comment.
President Donald Trump's eldest son eagerly agreed in June 2016 to meet Ms Veselnitskaya, a woman he was told was a Russian government lawyer who might have damaging information about Democratic White House rival Hillary Clinton, according to emails released by Trump Jr.
Ms Veselnitskaya has said she is a private lawyer and has never obtained damaging information about Clinton.
Dmitry Peskov, a spokesman for the Kremlin, has said she had "nothing whatsoever to do with us".