What do we know about the protests in Melbourne, and how did the numbers grow?

Protests in Melbourne over two days that again turned violent on Tuesday afternoon began with construction workers rejecting vaccine mandates, but were then boosted by anti-lockdown and anti-vaccination groups on social media, experts have said.

A small group of protesters gathered outside the Construction, Forestry, Maritime, Mining and Energy Union (CFMEU) headquarters on Monday to protest against vaccine mandates, and it is understood that numbers rose after anti-lockdown Telegram groups put the call out.

Politicians and union leaders, including CFMEU branch secretary John Setka and the former Labor leader Bill Shorten, blamed far-right groups for driving the protest and the violence that ensued. Shorten labelled the protesters “man-baby Nazis”.

Related: Victoria Covid update: police arrest 44 people and fire rubber pellets during Melbourne construction protests

But when the protesters returned on Tuesday, less than 24 hours after Victorian premier Daniel Andrews shut down the sector for two weeks, it was unclear who had organised the protest, and who was joining it.

The Australian Council of Trade Unions secretary, Sally McManus, said the protest had been “called for, led, and promoted” by anti-vaccination and far right groups.

“What they’re doing is jumping on it to cause division and, in the end, that’s going to lead to a situation that we’ll be in lockdown longer,” she said.

“People can either take a role which is about uniting people and getting us through to the other side, or they can go about sowing lies and hate and division. Unfortunately, that’s what some of these extremists are doing.”

The national secretary of the CFMEU construction and general division, Dave Noonan, told the ABC on Tuesday hi-vis gear was being handed out to people to make them look like construction workers.

“This is really a group of rightwing extremists who have really tried to decide to divide the community when we are in immense strain and under immense pressure through the health crisis due to Covid, but also with people who are understandably upset, rattled, and over repeated lockdowns,” he said.

Elise Thomas, an analyst and researcher for the Institute for Strategic Dialogue who specialises in misinformation, said anti-lockdown groups were clearly taking a lead on Tuesday.

“I think there’s a difference between yesterday’s protest versus today’s on the organisational front, insofar that today the protest was obviously being promoted by a whole bunch of different anti-lockdown groups.

“I am not aware of any good evidence to suggest that organised far-right groups were involved in planning the protest [on Monday]. My sense is the protest started in some other way, likely offline, and then went out on the big Telegram anti-lockdown groups around 10am.”

Thomas said it was difficult to draw a clear distinction between people from anti-lockdown groups and construction workers.

“There’s not a neat binary between tradies and anti-lockdown or conspiracy groups, there clearly are people who are both,” Thomas said.

Tom Tanuki, an anti-fascist activist and researcher, agreed.

“I think it needs to be said that many were construction industry people too, or related … There’s non-union construction people there. There’s anti-vaxxers dressing up in thematic hi-vis there. It’s a real mixed bag.”

Construction sites have been the source of more than 330 Covid-19 cases in the current Melbourne outbreak of the Delta strain, but also a source of increasing disaffection among workers about the restrictions being put in place to contain the outbreaks.

Last week construction workers set up tables and chairs in the middle of the road in Melbourne to protest against being denied access to their tearooms.

Posters for protests targeting the construction industry have been circulating in anti-lockdown Telegram groups. One of the largest focused on Melbourne encouraged people to turn up to the Monday protest, and urged those attending to wear hi-vis, regardless of whether they worked in the industry.

As suggested by the direction of the protest on Tuesday – which did two laps of the city from the CFMEU to parliament to Flinders Street station before heading to West Gate Bridge – the movement currently lacks any clear organisation.

However, the way the message spread is much clearer – on Telegram groups and, above all, on Facebook.

A Facebook livestream of Monday’s protest had 30,000 viewers at one point. On Tuesday, it reached 70,000 simultaneous viewers.

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Some in the crowd certainly appeared to have far-right sympathies. There was one who identified as a Proud Boy, someone who complained about the New World Order while wearing a Donald Trump hat, two Trump flags were waved by people in hi-vis, and a former member of the United Patriots Front was spotted in the crowd on the West Gate Bridge.

But for the most part, the thousands who gathered were not identifiably aligned with any political group or message, save for being anti-Daniel Andrews and anti-mandatory vaccination.

Some said they had been CFMEU members for decades, others were clearly young tradies. Some hi-vis gear had cement stains, others looked as they were wearing it for the first time. Many were keen to stress they had no connection to the far right.

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Tanuki said it was much too simple to label those attending the protests as neo-Nazis or far-right agitators.

“I don’t agree with Setka saying they’re all ‘neo-Nazis’, this is dumb or sloppy or inaccurate. But they’re sent out by anti-vaxxers; that’s what they are. And their immersion in the anti-lockdown scene makes them predisposed to the manipulations of many of these influencers ... some of whom are neo-Nazis.”