The Russian hacking unit that tried to interfere in the United States presidential election has been targeting conservative US think tanks, Microsoft said.

Acting on a court order, last week the company seized control of six fake websites involved in such efforts, which also involved a site that mimicked the US Senate, Microsoft President Brad Smith said in a blog post on Monday.

The hackers were linked to the Russian military unit formerly known as the GRU, Smith wrote.

The idea was to have people think they were accessing links managed by these US political groups but redirect them to fake ones run by the hackers so passwords and other information could be stolen.

Smith said one such site appeared to mimic that of the International Republican Institute, which promotes democratic principles and whose board includes Republican senators, among them John McCain, who have been critical of President Vladimir Putin.

Another is similar to the domain used by the Hudson Institute, which hosts prominent discussions on topics including cybersecurity.

“We're concerned that these and other attempts pose security threats to a broadening array of groups connected with both American political parties in the run-up to the 2018 elections,” Smith wrote.

Experts said the aim was to go after anyone who opposes Putin.

“This is another demonstration of the fact that the Russians aren't really pursuing partisan attacks. They are pursuing attacks that they perceive in their own national self-interest,” Eric Rosenbach, the director of the Defending Digital Democracy project at Harvard University, told The New York Times.

“It's about disrupting and diminishing any group that challenges how Putin's Russia is operating at home and around the world,” Rosenbach added.