WASHINGTON — The Trump campaign’s interactions with Russian intelligence services during the 2016 presidential election posed a “grave” counterintelligence threat, a Senate panel concluded Tuesday as it detailed how associates of Donald Trump had regular contact with Russians and expected to benefit from the Kremlin’s help.

The panel’s almost 1,000 page report, the fifth and final one from the Republican-led Senate intelligence committee on the Russia investigation, describes in detail how Russia launched an aggressive, wide-ranging effort to interfere in the election on Trump’s behalf. It says Trump associates were eager to exploit the Kremlin’s aid, particularly by maximizing the impact of the disclosure of Democratic emails that were hacked by Russian military intelligence officers.

The findings released Tuesday mark the culmination of a bipartisan probe that produced what the committee called “the most comprehensive description to date of Russia’s activities and the threat they posed.” The investigation spanned more than three years as the panel’s leaders said they wanted to be as thorough as possible in documenting the unprecedented attack on U.S. elections.

The findings echo to a large degree those of special counsel Robert Mueller’s Russia investigation, with the report’s unflinching characterization of furtive interactions between Trump associates and Russian operatives contradicting the Republican president’s claims that the FBI had no basis to investigate whether his campaign was conspiring with Russia. Trump has called the Russia investigations a “hoax.”

In this March 21, 2018 file photo, Senate Intelligence Chairman Richard Burr, R-N.C., right, accompanied by Committee Vice Chairman Mark Warner, D-Va., left, before a Senate Intelligence Committee hearing on election security on Capitol Hill in Washington. The Senate intelligence committee has concluded that the Kremlin launched an aggressive effort to interfere in the 2016 presidential contest on behalf of Donald Trump. The Republican-led panel on Tuesday released its fifth and final report in its investigation into election interference. AP Photo/Andrew Harnik

While Mueller’s was a criminal probe, the Senate investigation was a counterintelligence effort with the aim of ensuring that such interference wouldn’t happen again.

The report was released as two other Senate committees, the Judiciary and Homeland Security panels, conduct their own reviews of the Russia probe with an eye toward uncovering what they say was FBI misconduct during the early days of the investigation. A prosecutor appointed by Attorney General William Barr, who regards the Russia investigation with skepticism, disclosed his first criminal charge on Friday against a former FBI lawyer who plans to plead guilty to altering a government email.

Among the more striking sections of the report is the committee’s description of the close professional relationship between former Trump campaign chairman Paul Manafort and Konstantin Kilimnik, whom the committee describes as a Russian intelligence officer.

“Taken as a whole, Manafort’s high-level access and willingness to share information with individuals closely affiliated with the Russian intelligence services, particularly Kilimnik, represented a grave counterintelligence threat,” the report says.

The report notes how Manafort shared internal Trump campaign polling data with Kilimnik and says there is “some evidence” that Kilimnik may have been connected to the Kremlin’s operation to hack and leak Democratic emails, though it does not describe that evidence. In addition, the report says that “two pieces of information” raise the possibility of Manafort’s potential connection to those operations, but what follows next in the document is blacked out.

Both men were charged in Mueller’s investigation, but neither was accused of any tie to the hacking.

A Manafort lawyer, Kevin Downing, said Tuesday that there is information that was sealed at the request of Mueller’s team “that completely refutes whatever the intelligence committee is trying to surmise.” He added: “It just looks like complete conjecture.”

Like Mueller, the committee reviewed a meeting that Trump’s oldest son, Donald Trump Jr., took in June 2016 with a Russian lawyer he believed to have connections with the Russian government with the goal of receiving information that he expected would be harmful to Clinton.

The Senate panel said that it assessed that the lawyer, Natalia Veselnitskaya, has “significant connections to the Russian government, including the Russian intelligence services,” as did another participant in the meeting, Rinat Akhmetshin. The panel said it uncovered connections that were “far more extensive and concerning than what had been publicly known,” particularly regarding Veselnitskaya.

The report also found no reliable evidence for Trump’s longstanding supposition that Ukraine had interfered in the election, but did trace some of the earliest messaging of that theory to Kilimnik. It said Russian-government proxies were “consistently spreading overlapping false narratives which sought to discredit investigations into Russian interference in the 2016 U.S. elections.”

The committee said that messaging campaign lasted from to “at least January 2020” — after the House had impeached Trump for pressuring Ukrainian officials to investigate the family of Democrat Joe Biden, who is now Trump’s general election opponent. During that effort, some Republicans, including Trump, argued that Ukraine was meddling, not Russia.

The report purposely does not come to a final conclusion, as Mueller did and as the House intelligence committee’s 2018 report did, about whether there is enough evidence that Trump’s campaign coordinated or colluded with Russia to sway the election to him and away from Democrat Hillary Clinton, leaving its findings open to partisan interpretation.

In this March 21, 2018 file photo, Sen. Marco Rubio, R-Fla., left, accompanied by Sen. Susan Collins, R-Maine, right, speaks before a Senate Intelligence Committee hearing on election security on Capitol Hill in Washington. AP Photo/Andrew Harnik

A group of Republicans on the panel submitted “additional views” to the report saying that it should state more explicitly that Trump’s campaign did not coordinate with Russia. They say the report is an “important contribution to the historical record” that shows “the Russian government inappropriately meddled in our 2016 general election in many ways but then-candidate Trump was not complicit.”

The acting GOP chairman of the panel, Florida Sen. Marco Rubio, signed on to that statement but the chairman who led the investigation, North Carolina Sen. Richard Burr, did not. Burr stepped aside earlier this year as the FBI was examining his stock sales.

Burr, who submitted the report before he stepped aside, often faced criticism from his GOP colleagues for working with Democrats on the probe and for calling in sensitive witnesses, such as Trump Jr.

Another Republican member of the panel, Maine Sen. Susan Collins, also did not sign on to the GOP statement.

Democrats on the panel submitted their own views, saying the report “unambiguously shows that members of the Trump campaign cooperated with Russian efforts to get Trump elected.”

Maine Sen. Angus King, an Independent who caucuses with Democrats, did not sign on to that statement, saying he believed the report should be bipartisan. But he said in an interview that he believes the report is a “warning.”

The report is “not a hoax,” King said. “It’s just one more set of facts that’s hard to ignore.”

Mueller concluded in his report issued last year that Russia interfered in the election through hacking and a covert social media campaign and that the Trump campaign embraced the help and expected to benefit from it. But Mueller did not charge any Trump associates with conspiring with Russians.

The Senate investigation also delved into areas of great interest to Trump that were not explored by Mueller. Those include the FBI’s reliance on a dossier of opposition research compiled by a former British spy whose work was financed by Democrats.

The committee did find faults with aspects of the FBI’s investigation, particularly with regard to its handling of opposition research on Trump’s ties to Russia that was compiled by a former British spy, Christopher Steele, whose work was funded by Democrats.

The committee found that the dossier “joined a stream of intelligence and investigative reporting” about Russian election interference even though the FBI never fully explored the credibility of its allegations. A separate investigation by the Justice Department’s inspector general also faulted the FBI for errors and omissions related to the Steele dossier as it applied for court permissions to secretly wiretap a former Trump campaign adviser named Carter Page

Rubio said in a statement that the committee was troubled that the FBI had been willing to use the dossier “without verifying its methodology or sourcing” as it applied for secret surveillance warrants against a former Trump campaign adviser.