Russian Twitter bots troll Speaker of the House of Representatives Paul Ryan

Bots linked to Russia have stepped up efforts to target Republican party members, say political activists.

Political activists have discovered that bots and trolls linked to Russia are seeking to influence US politics yet again, in the hopes of pressuring the House Speaker Paul Ryan to resign.

The Alliance for Securing Democracy, a transatlantic project run by former US national security officials and funded by nonpartisan American public policy think tank German Marshall Fund of the United States (GMF), has observed an unusual spike in activity on Twitter over the last 48 hours.

Twitter accounts known to be Russian-linked bots have been spamming the hashtag #ResignPaulRyan, causing it to surge in popularity. Meanwhile, Ryan toured flood-damaged areas in Wisconsin and tried to allay concerns of Republican voters.

The Alliance was set up in 2016 following repeated allegations by US intelligence agencies that Russia had interfered with the US presidential election by releasing internal emails from the Democratic National Committee and Hillary Clinton's campaign Chairman John Podesta.

The organisation aims to help defend against and deter any attempts made by Russia or other state actors to undermine American democracy, and one of its strategies is the development of a real-time dashboard that tracks social chatter, top trending news stories and popular retweets.

The social media attack on Ryan follows last week's vote in Congress to beef-up sanctions against Russia.

There was overwhelming bipartisan support for the new measures in response to Russia's interference in the 2016 US election, as well as its human rights violations, annexation of Crimea and military operations in eastern Ukraine.

The move infuriated Moscow which responded by stripping 755 staff members and two properties from US missions in the country.

Ryan wasn't the only member of Trump's party to face countless bots demanding his removal. A campaign calling on the president to fire National Security Adviser H.R. McMaster - who is laso perceived as being anti -Russian - received widespread support from bots and trolls over the last several days using the hashtag #FireMcMaster.

Other key hashtags relating to US politics spiking include "WhyTrumpWon", "TrumpTV", "Fake" and "ReasonsNotToSeeAlGore'sMovie", slamming former US vice president Al Gore's new climate change documentary An Inconvenient Sequel: Truth to Power.