WASHINGTON: The chairman of President Donald Trump's 2016 election campaign secretly shared campaign information with a Russian intelligence officer, posing a "grave" espionage threat to the United States, a US Senate report said Tuesday.

Before and during his nearly six months on the Trump campaign, Paul Manafort, a veteran Republican political consultant, directly and indirectly communicated with Konstantin Kilimnik, identified as a Russian intelligence officer, and Oleg Deripaska, a Russian oligarch close to Vladimir Putin, the Senate Intelligence Committee said.

"On numerous occasions, Manafort sought to secretly share internal campaign information with Kilimnik," including polling and strategy details, it said.

While the reason for the sharing was not clear, the report said, it noted that it took place just as Russian GRU intelligence and a government-linked social media operation actively sought to tilt the election toward Trump.

Manafort "was secretly communicating with a Russian intelligence officer ... while the Russian intelligence operation to assist Trump was ongoing," the report said.

"Taken as a whole, Manafort's high-level access and willingness to share information with individuals closely associated with Russian intelligence services, particularly Kilimnik and associates of Oleg Deripaska, represented a grave counterintelligence threat."

The Senate report, the final product of a three-year investigation into Russian election meddling in 2016, described numerous incidents in which the Trump campaign actively sought the help of Moscow and WikiLeaks to damage the campaign of Trump rival Hillary Clinton.

The report came as US intelligence has warned of active Russian attempts to interfere in the current presidential race in Trump's favor.