Victorian Premier Jacinta Allan said the chief commissioner had informed her a number of arrests had been made after the protest outside the Land Forces defence exhibition at Melbourne’s convention centre turned ugly on Wednesday.
“What we are seeing is a potentially dangerous and dynamic situation,” she said at state parliament.
Wheelie bins were set on fire and thrown towards police as the protest moved to the Spencer Street Bridge about 9.15am.
The Land Forces International Land Defence Exposition hosts military, defence, government, scientific and industry delegations from around the world and runs to Friday.
The Malinauskas Government said a record 67 exhibitors from SA will feature on the Defence SA stand, “cementing our place as the Defence State”.
As tensions flared heavily armed police set off canisters of tear gas and used pepper spray foam to control the crowd. The gas was released on the bridge, triggering loud bangs, with dozens of protesters and attendees being treated.
Trams were disrupted and motorists delayed as protesters blocked the opening of the event at 9am, with dozens of police creating a barricade to make way for attendees to enter, with protesters flanking either side.
Activists threw water and eggs and yelled “war pigs” or “get a real job” at the attendees as they walked along Yarra Promenade to enter the expo.
“Shame on you, how does it feel to murder babies,” one group of protesters yelled in unison.
Some protesters fought with police, with one officer left with a bleeding face, while a cameraman was hit with pepper spray.

Victoria Police expected today’s protest to be its biggest operation in more than two decades and deployed officers from around the state to the convention centre.
Yarra Trams warned commuters of disruptions to several city-bound services while the citybound exit of the West Gate Freeway was closed at Montague St, causing delays for those using both the West Gate and Bolte Bridges.

Disrupt Land Forces spokeswoman Jasmine Duff said the protest was triggered by the government’s stance on the conflict in the Middle East.
“We’re protesting to stand up for all those who have been killed by the type of weapons on display at the convention,” she said.
“Many of the weapons inside the convention centre are advertised as battle-tested. In the context of Israeli weapons firms, which are present, this means tested through killing civilians in Gaza.”