This file photo taken on April 17, 2017 shows Donald Trump, Jr., son of US President Donald Trump, attending the 139th White House Easter Egg Roll on the South Lawn of the White House in Washington, DC. (SAUL LOEB / AFP)

WASHINGTON - US President Donald Trump's oldest son, Donald Trump Jr., has agreed to testify privately to the Senate Judiciary Committee as it looks into allegations of Russian interference in the 2016 US election, CNN reported on Tuesday, weeks after he was invited to testify in public at a hearing in July.

Spokesmen and spokeswomen for the committee's leaders did not immediately respond to requests for comment on the report.

CNN also reported that Special Counsel Robert Mueller had issued subpoenas to Melissa Laurenza, an attorney with the Akin Gump law firm, who formerly represented Trump's former campaign manager, Paul Manafort, and to Jason Maloni, a Manafort spokesman.

CNN said Maloni and a spokesman for Mueller declined comment and that Laurenza referred questions to a spokesman who did not immediately comment.

Russia has loomed large over the first six months of the Trump presidency. US. intelligence agencies have concluded that Russia worked to tilt last year's presidential election in Trump's favor. Mueller, who was appointed special counsel in May, is leading the investigation, which also examines potential collusion by the Trump campaign with Russia.

Several congressional committees are also looking into the matter.

Moscow denies any meddling. Trump denies any collusion by his campaign, while regularly denouncing the investigations as political witch hunts.