An American senator has alleged that Russia attempted to undermine the 2016 US presidential election with a propaganda campaign "on steroids".

Virginia Senator Mark Warner made the accusations on Thursday during a US Senate Intelligence Committee hearing.

Warner, who was a technology executive before entering politics, described a sweeping Russian campaign using trolls and botnets, or networks of hacked or infected devices, to disseminate large amounts of disinformation.

"This Russian 'propaganda on steroids' was designed to poison the national conversation in America," Warner said.

Warner, a Democrat, also alleged Russian news organisations such as RT and Sputnik "produced and peddled" disinformation to American audiences in hopes of damaging former secretary of state Hillary Clinton, who was seen as the frontrunner in the 2016 presidential vote.

Russian President Vladimir Putin denied the accusations on Thursday, calling them "lies". When asked if Russia interfered in the US vote Putin said, "Read my lips: No."

WATCH: Wiretaps, hacks and spin in Donald Trump's America

President Donald Trump should uncover Russian activities during the election, Warner said, even as he criticised the US leader for what he called "wild and uncorroborated accusations" that his campaign was wiretapped.

Warner's fellow Democrat Senator Ron Wyden also urged the Senate to "follow the money" on Russia, adding that real estate deals and money-laundering might mean the "Russian government may be only a step or two away" from American institutions.

In the same hearing, cyber-security expert Clint Watts said Moscow-directed disinformation campaigns were "strategically leaked" to damage the presidential prospects of candidates from both political sides.

Watts of the Foreign Policy Research Institute told Senator Marco Rubio that his presidential campaign was targeted by Russia.

'Trolling networks'

Rubio was one of the rivals of then-candidate Donald Trump in the Republican presidential nomination.

Rubio on Thursday confirmed that his former campaign advisers were unsuccessfully targeted by cyber-attacks in July 2016, and again within the past 24 hours.

Watts also said that in the past week social media campaigns have targeted House Speaker Paul Ryan.

He did not offer details but alleged the recent activities show Russia is continuing to seek further unrest among US democratic institutions, leaders, and their constituents.

Later Watts told reporters the "trolling networks", which his research institute monitors, were disseminating propaganda about dissension in the ranks of the Republican Party over the vote for Ryan as Speaker of the House.

There was no immediate comment from Ryan's office.

Al Jazeera's James Bays, reporting from Washington DC, said "the storm is just growing" in the US capital with different investigations looking into Russian spying and alleged links to the Trump campaign.

Putin dismissed what he called "endless and groundless" accusations of Russian meddling in the election. He described the allegations as part of a domestic political struggle in the United States.

Trump has also dismissed suggestions of links with Russia as Democratic Party sour grapes after his surprise November defeat of the party's candidate, Clinton.