London: An astonishing piece of propaganda linking the upcoming Brexit vote in Britain to the Orlando nightclub massacre has attracted fury - even from diehard 'Leave' supporters such as Nigel Farage.

On Monday the Leave.EU group, which supports britain exiting the European Union, tweeted: "The free movement of Kalashnikovs in Europe helps terrorists. Vote for greater security on June 23. Vote Leave."

Attached was a piece of campaign literature showing a group of IS fighters, with the slogan "Islamist extremism is a real threat to our way of life. Act now before we see an Orlando-style atrocity here before too long."

Below, smaller text encouraged the reader to join the movement.

Leave.EU is a grassroots movement funded by UKIP donor Arron Banks. It is not the official Out group but is an influential voice in the hard-fought referendum campaign over Britain's EU membership.

The tweet was deleted, but then re-posted some hours later. It attracted predictable responses online condemning its tone, content and timing.

Among the voices calling for it to be withdrawn were pro-Leave campaigners, including a 'Leave EU Holborn' account and a regional UKIP official, David Gunn.

Another pro-Leave Twitter user, Andy Jardine, complained "I'm for vote leave but this type of scaremongering does the leave campaign no favours… it's pure Donald Trump".

UKIP leader Nigel Farage said the tweet had "nothing to do" with him, and had been approved by an "office junior".

"I just think generally after a horrible tragedy it's best to wait a bit and keep quiet," he said.

And Brexit-backing former Conservative minister Iain Duncan Smith said it was "completely pointless to make something out of a tragedy in America that has nothing to do with this debate", telling BBC radio: "I abhor anybody that tries to make capital out of that."

He distanced Vote Leave – the official Brexit campaign – from Leave.EU, saying they had "nothing to do" with each other.

However he added that "Europol has made the point to the Home Secretary quite recently that unless we control migration there are threats to security, that's a fact of life".

The tweet was also condemned by pro-Remain politicians including home secretary Theresa May who called it "utterly irresponsible".

Will Straw, the director of Britain Stronger in Europe, said it was "Trump-ist scaremongering".

And Labour shadow foreign secretary Hilary Benn said the image was shameful and cowardly.

A few minutes after re-posting the deleted tweet, the Leave.EU account added another on the same theme.

"Terrorist's greatest weapon:" it said, over an image of European Union passports.

pic.twitter.com/hZvB6WjOTK— LEAVE.EU (@LeaveEUOfficial) June 13, 2016

Recent polls have the Leave campaign pulling ahead of Remain, in a campaign that is becoming increasingly intense and acrimonious.

Both sides have accused each other of scaremongering and lying about the impacts of leaving or staying in Europe.