Fancy Bear has ties to Russian military intelligence which infiltrated servers during the last presidential race Sean Gallup/Getty Images

Hackers linked to Russian military intelligence launched a sophisticated cyber operation against conservative think tanks in the United States ahead of November’s midterm elections.

News of the attack came as Jeremy Hunt was on his first visit to Washington as foreign secretary. He will today challenge the European Union to “stand shoulder to shoulder” with the US by imposing new sanctions on Russia over the Salisbury novichok poisoning. Mr Hunt’s appeal follows an announcement of a new tranche of US sanctions triggered by a decades-old law on the use of chemical weapons rather than a political decision by the Trump administration.

In the latest cyberoffensive, the Russian attackers created scores of websites that mimicked groups critical of President Putin in an apparent attempt to steal…