Russia's FSB spy agency was a client of the Russian lawyer at the center of U.S. probes into Moscow's alleged attempts to meddle in the presidential election, media reported on July 21.
Russian court documents show that Natalya Veselnitskaya represented a military unit operated by the FSB in a legal dispute over ownership of property in Moscow between 2005 and 2013, AP and Reuters reported.
The Federal Security Service, or FSB, is the successor to the Soviet-era KGB intelligence agency and was headed by Vladimir Putin before he became president of Russia.
Former U.S. President Barack Obama last year sanctioned the FSB for what he said was its role in hacking the election.
Veselnitskaya has denied being employed by Russian intelligence services or the government.
She was a central figure in a June 2016 meeting at Trump Tower in New York with U.S. President Donald Trump's eldest son, his son-in-law, and campaign manager that has become a top subject of investigation in Congress and at the Justice Department.
She sought out the meeting with Donald Trump Jr. and was introduced by a go-between as a "Russian government lawyer" who had information provided by the Russian government that would be damaging to Trump's rival Hillary Clinton.
E-mails show Trump Jr. eagerly agreed to the meeting and brought along Jared Kushner, Trump's son-in-law who is now a senior White House official, as well as then-Trump campaign chairman Paul Manafort.
Several other Russians were at the meeting, and one of those told AP that Veselnitskaya provided Trump Jr. with a portfolio showing illegal Russian campaign contributions to the Democratic National Committee.
Apparently in light of such reports, the special counsel that is investigating possible collusion between Russia and the Trump campaign asked the White House on July 21 to preserve any records and documents that came out of the meeting.
Committees of Congress have made similar requests and investigators in both branches of the U.S. government are also seeking to interview participants in the meeting.
Veselnitskaya has said she is prepared to testify on what transpired at the meeting, to put to rest what she called "mass hysteria" about Russian meddling in the election.
On July 21, she made light of the reports showing she once represented the FSB in court, saying on Facebook that "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."
Veselnitskaya added that she also had U.S. citizens as clients.