Washington (AFP) -

A Senate committee released thousands of pages of congressional testimony Wednesday from its probe into a meeting at Trump Tower between US President Donald Trump's son and Russians who had promised incriminating material on Hillary Clinton.

Donald Trump Jr, in testimony released by the Republican-led Senate Judiciary Committee, says he did not tell his father ahead of time about the meeting with a Kremlin-connected lawyer five months ahead of the November 2016 presidential election.

The June 9, 2016 meeting with Natalia Veselnitskaya was also attended by then-Trump campaign manager Paul Manafort and Trump's son-in-law Jared Kushner.

It has fueled speculation about possible collusion between the Trump campaign and Russia and is believed to be of interest to special counsel Robert Mueller, who is investigating Russian meddling in the election.

Trump has repeatedly denied his campaign colluded with Russia to get him elected and has denounced Mueller's investigation as a "witch hunt."

The Trump Tower meeting was arranged by a music promoter, Rob Goldstone, who reached out to Trump Jr saying he had "official documents and information that would incriminate Hillary and her dealings with Russia and would be very useful to your father."

Trump Jr responded "I love it" when first offered the political "dirt" on Clinton, the Democratic presidential nominee.

Trump Jr has said since that no "meaningful information" was offered and the meeting focused mostly on the issue of adoptions of Russian children.

In his testimony, he said he did not know whether his father was directly involved in explanations about the meeting that reportedly contained discrepancies, but acknowledged the president "may have" influenced the messaging through then-White House communications assistant Hope Hicks.

Asked if Trump's comments through Hicks were incorporated into the final explanation of the meeting, Trump Jr said "I believe some may have been."

Among the 2,600 pages of documents released Wednesday was the full transcript of Trump Jr's testimony.

In a statement to US media, Trump Jr said he appreciated "the opportunity to have assisted the Judiciary Committee in its inquiry."

"The public can now see that for over five hours I answered every question asked and was candid and forthright with the committee," he said.

Manafort, who has been charged with a variety of non-campaign related offenses as a result of Mueller's investigation, was not interviewed by the panel.

Senate Judiciary Committee chairman Chuck Grassley said he was releasing the documents so "Americans can now review this unfiltered information and arrive at their own conclusions."

- 'Helping' Trump, 'hurting' Clinton -

Committee Democrats said the June 2016 Trump Tower meeting "confirms that the Trump campaign was willing to accept Russia's assistance."

"Their efforts to conceal the meeting and its true purpose are consistent with a larger pattern of false statements about the Trump campaign's relationship with Russia," they said in a statement. 

They said the committee found evidence of "multiple contacts" between the Trump campaign and Russian government officials or their intermediaries, "including offers of assistance and purported overtures from (Russian President) Vladimir Putin, which warrant further investigation."

Separately Wednesday, the Senate Intelligence Committee said it completed its review of Russian influence on the election and concluded it agreed with the US intelligence community's assessment that Moscow sought to sway the vote in Trump's favor.

The panel's chairman, Senator Richard Burr, said in a statement that after 14 months of reviewing tradecraft and analytic work, "we see no reason to dispute the conclusions" by the intelligence community.

Top committee Democrat Senator Mark Warner added that "the Russian effort was extensive, sophisticated, and ordered by President Putin himself for the purpose of helping Donald Trump and hurting Hillary Clinton."

The bipartisan conclusion countered the assessment of House Intelligence Committee Republicans, who had accused intelligence agencies of failing to use appropriate "tradecraft" when those agencies determined that Russia backed Trump's candidacy.