Pro-Palestine and anti-war protesters are planning a third straight day of demonstrations outside the entrance of the Melbourne Convention and Exhibition Centre which is hosting the Land Forces weapons convention.
Police were out in force again early on Thursday, maintaining no-go lines near the convention centre ahead of visitors to the expo arriving.
Chaotic scenes between protesters and police broke out on Wednesday, sparked by the government's stance on the conflict in the Middle East with many weapons on display inside the convention used on civilians in Gaza.
Police returned fire with rubber bullets, tear gas and flash bang devices. (Con Chronis/AAP PHOTOS)
Wheelie bins were set alight and thrown towards police barricades, while horse manure, food-grade acid, glass bottles and baked beans can "missiles" were launched at officers.
Riot officers returned fire on the 1500 demonstrators with rubber bullets, tear gas and flash bang devices.
Police said 27 officers were treated for minor injuries, while rally organiser Caroline Da Silva said there were "eight to 10 times" the number of activists injured in the melee.
Despite that she vowed demonstrators would regroup, nurse their injuries and be back on Thursday.
"We are not deterred," Ms Da Silva said.
"People are very angry about this expo. It's particularly on the nose given there's already very strong community sentiment about the genocide in Gaza.
"To be running a weapons expo and going, 'hey, hey, come and make some billion dollar deals' to buy more murder tech in the middle of that, it's pretty off".
Police Commissioner Shane Patton urged protesters to reflect on their conduct and to consider whether their actions would garner support for their cause.
"We will be prepared for any event for the duration of this this conference, but I hope it doesn't occur again tomorrow," he said.
Forty-two people were charged with assaulting, hindering and obstructing police. (Joel Carrett/AAP PHOTOS)
"If people come to protest - we urge them not to - but if they do, and they come and do so peacefully, happy days.
"But if they break the law, we will hold them to account."
Amid the violent scenes, a coalition of human rights groups have written to the Victorian government calling for the prohibition of explosive devices, pepper spray and police horses at protests, which they say is an unnecessary use of force.
Forty-two people were arrested and charged with assaulting, hindering and obstructing police, arson and blocking roadways.
The activists will rally outside the offices of defence contractors Hanwha Defence and Elbit Systems before holding a vigil for Gaza.
