Reader comments sections of prominent western news websites have been infiltrated by pro-Russian trolls seeking to manipulate the picture of public opinion, researchers believe.

The major influence operation is said to have targeted 32 media outlets online across 16 countries, including the Daily Mail, Daily Express, The Times, Fox News and The Washington Post.

Almost 250 stories were found to contain provocative pro-Kremlin or anti - Western sentiments in the comments about matters of relevance to Russia - such as tensions in Crimea - since a probe began in April.

The ongoing campaign is thought to have escalated since 2018, but more recently it has exploited the US and UK withdrawal from Afghanistan.