At least 30 governments around the world are employing "keyboard armies" to spread propaganda and attack critics, a report has found.

The annual "Freedom on the Net" report from the think tank Freedom House showed that the spread of online misinformation went far beyond Russia and China to almost half of the 65 countries studied in the report.

It found governments including Mexico, Saudi Arabia and Turkey were using "paid pro-government commentators" to shape opinions online, often to give the impression of grassroots support for government policies.

They include paid commentators, trolls, bots and fake news, which are used to harass journalists, flood social media with fabricated opinions and erode trust in other media. The report's authors warned that the techniques had become far more advanced and widespread in recent years, and said fake news had been employed in an attempt to influence elections in 18 countries, including the UK.

"The use of paid commentators and political bots to spread government propaganda was pioneered by China and Russia but has now gone global," said Michael Abramowitz, Freedom House's president. "The effects of these rapidly spreading techniques on democracy and civic activism are potentially devastating."