MELBOURNE — Dozens of people have been arrested after clashing with police at an anti-war demonstration in Melbourne.

Police said they were "appalled" by the actions of some demonstrators targeting a military hardware sales show in Australia's second largest city, accusing them of pelting officers with rocks, manure and bottles filled with acid.

By contrast, protestors said officers were heavy-handed and responded with flashbang grenades and irritant sprays to control the hostile crowd.

Prime Minister Anthony Albanese condemned the violence, saying Australians had a right to protest - but had to do so in a peaceful manner.

"You don't say you're opposed to defense equipment by throwing things at police," Mr Albanese told local media. "They've got a job to do and our police officers should be respected at all times."

Authorities said about 1,200 people had taken part in the demonstration targeting the Land Forces International Land Defence Exposition, many of whom sported Palestinian flags and sang pro-Palestinian chants.

Police had anticipated unrest ahead of the event, which is expected to draw over 1,000 corporations from 31 countries in the coming days. The expo, which is not open to the public, brings together military, defence, government, scientific and industry delegations from around the world.

Local media reported military artillery, trucks and semi-automatic weapons have been on display during the convention. Activists had said they were protesting as they claim many of the weapons on-show have been used by Israeli forces in Gaza.

Footage showed dumpsters being pushed towards police lines during the clashes, with multiple fires being lit across the city and demonstrators blocking roads. One activist climbed on top of a stationary truck at a set of traffic lights.

About two dozen police officers were treated for injuries sustained during the unrest, Victoria state Police Chief Commissioner Shane Patton said. He told reporters 39 people had been arrested in Wednesday's clashes.

Commissioner Patton accused those behind the violence of being "hypocrites", adding demonstrators said they wanted to "protest against war, so presumably [were] anti-violence".

But his officers have been criticized by demonstrators for being overly heavy-handed. Organizers said they were "appalled at the level of violence directed against community members protesting for peace".

"The police have been extremely violent towards protestors today, actually in an unprecedented way," Jasmine Duff, an activist from Students for Palestine, said.

"They used flashbang grenades, they’ve been pepper spraying people very viciously."

Some journalists reported seeing police fire rubber bullets, but Commissioner Patton said the projectiles were actually hard foam baton rounds.

Officials say around A$10m (£7.6m) was spent on deploying extra police to protect the event, with officers reportedly drafted in from New South Wales.

"It's absolutely outrageous that reportedly $10 million has been spent on this police presence," one of the protest group organizers, Anneke Demanuele from Students for Palestine, told ABC News.

Victoria Premier Jacinta Allan defended the state's handling of the event, saying delegates had the right to gather in Melbourne.

"Any industry deserves the right to have these sort of events in a peaceful and respectful way," she said. — BBC