Former CIA director John Brennan (file photo/CGTN)

Former CIA director John Brennan told a congressional hearing on Tuesday that he believed Russia tried to interfere in the US elections, but he couldn’t confirm whether there was a conspiracy between the Trump campaign team and Russia.

He also said that he had noticed contact between Russian officials and people involved in the Trump campaign last summer, and he personally warned the head of Russia's FSB security service, Alexander Bortnikov, that such interference could harm US-Russia ties in a phone call on August 4.

Brennan added that he briefed former President Barack Obama and other top officials and discussed the issue with congressional leaders in August and September.

His words become the most direct recognition by a current or former US official yet that Russia sought to help Trump defeat Hillary Clinton in the 2016 election.

However, Trump has always denied any collusion. A White House official told reporters the hearings showed “there is still no evidence of any Russia-Trump campaign collusion."

Brennan's testimony before a House panel in an open hearing is a part of the investigation into whether the Russian intelligence agency intervened in the 2016 US presidential election, an issue which has been a major focus of public attention since Trump's dismissal of former FBI director James Comey earlier this month.