Vandals have reportedly targeted Auckland music venue, the Powerstation, after it cancelled an event by Canadian provocateurs Lauren Southern and Stefan Molyneux.

"Coward Station Free Speech - Eulogy Tour", was scrawled on the venue as graffiti, Newshub reports.

Powerstation owner Peter Campbell cancelled the alt-right Canadian pair's speaking event shortly after it was announced on social media.

While the venue said it simply didn't want to host the pair, there were also claims on Twitter on Saturday by someone claiming to have called in a bomb threat.

The person who posted it has since told the Herald the claim was made as a joke, has been taken "out of context" and was "never serious".

Auckland mayor Phil Goff also earlier barred Southern and Molyneux from using publicly funded venues for their talks after promoters had booked Takapuna's Bruce Mason Centre.

Goff said the pair weren't welcome in Auckland's multicultural and tolerant society.

Following his comments, the Free Speech Coalition was formed to raise money to help the pair continue their Auckland tour and file legal action against Goff.

Minister of Justice Andrew Little said it was clear Molyneux and Southern had "misled people" in trying to secure the Powerstation venue for their talk.

"Their message is insidious, it's nasty and of course you can say anything in the interest of freedom of speech but to just attempt to sow a destructive message."