MOSCOW — The Russian lawyer who met with Donald Trump Jr. last year after his father had won the Republican nomination for president had once represented Russia’s top intelligence agency in court, according to at least two public records.

The lawyer, Natalia V. Veselnitskaya, who is now at the center of the political intrigue over the Trump campaign’s possible collusion with Russia during Donald J. Trump’s presidential campaign, represented a military unit founded by the Russian Federal Security Service in 2002, publicly available records show.

The service, known as the F.S.B., is the successor agency to the K.G.B. and was once headed by President Vladimir V. Putin of Russia.

Ms. Veselnitskaya insisted after her June 2016 meeting with Mr. Trump’s son was first reported by The New York Times two weeks ago that she had no ties to the Kremlin and never worked for the Russian government. A Kremlin spokesman, Dmitri S. Peskov, has said Ms. Veselnitskaya “has nothing to do with us.”