Fake Twitter accounts created by a Russian propaganda unit made a determined, co-ordinated attempt to interfere during the EU referendum, Sky News can reveal.
A detailed analysis of Twitter accounts identified by the US senate as being linked to the Kremlin shows this activity before, during and after the Brexit vote in 2016.
However, although co-ordinated, Russian activity appears to be at a much lower level than in the US presidential elections.
The analysis was carried out by Yin Yin Lu, a researcher at the Oxford Internet Institute.
Ms Lu cross-referenced a pre-existing database of 22.6 million tweets she created last year with the 2,752 accounts identified as creations of the Russian Internet Research Agency by the US senate.
She found 416 tweets from the Russian usernames from March to July 2016, including during the referendum period itself.
Ms Lu told Sky News: "First of all the number of these tweets is important to highlight. So there's about 400 tweets here out of 22.6 million. That is a very infinitesimal fraction. So the word interference is perhaps a bit exaggerated."
However, those accounts appear to have co-ordinated strategically, retweeting each other to amplify their message and making much more use of photos and videos than normal Twitter users during the same period.
"There's some kind of network happening here," Ms Lu said.
One of the accounts that most frequently tweeted was @TEN_GOP, or Tennesse GOP. The account had more than 16,008 followers before it was suspended by Twitter.
It tweeted consistently pro-Leave tweets, including:
- "All Muslims of UK praying to #remain.. #Leave will mean disaster for them #Brexit #EURef"
- "'Leave' overperforms 'Remain'! Winston Churchill would be proud of you! #EURef: #Brexit…"
- "Is London done? Or they have chance? #BanIslam #Brexit"
Theresa May publicly warned Russia about election interference in a speech at Mansion House, saying: "I have a very simple message for Russia. We know what you are doing. And you will not succeed."
The Russian embassy made this statement: "The assertions are not brand new, but the main common point behind them is the irresponsible and groundless nature of accusations against Russia."
A Twitter spokesperson said: "Twitter recognises that the integrity of the election process itself is integral to the health of a democracy.
"As such, we will continue to support formal investigations by government authorities into election interference where required."