Anti-war protesters clash with police at Melbourne defence expo

Anti-war protesters and police clashed outside a defence exhibition in Australia's second-largest city of Melbourne on Wednesday, with police using sponge grenades, flash-bang devices and irritant sprays to control parts of the hostile crowd.

Police were pelted with rocks, horse manure and bottles filled with liquid as they tried to protect attendees of the expo, some of whom were assaulted by protesters, a Victoria state police spokesperson said in a statement.

Two dozen police officers required medical treatment and 33 people had been arrested for offences including assaulting, obstructing or hindering police, arson and blocking roads, police said. 

"Victoria police is appalled at the behaviour of some of the protesters in attendance," the police spokesperson said.

"Some police have been spat at by protesters, whilst other officers have been sprayed with a liquid irritant, some of which has been identified as acid."

Protesters lit fires in the street, disrupted traffic and public transport, while projectiles were thrown at several police horses but no serious injuries were reported, police said.

About 1,200 people attended the protest outside the venue hosting the biennial Land Forces International Land Defence Exposition, authorities said.

Many chanted pro-Palestine slogans through loud speakers and waving Palestine flags while dumpsters were pushed towards police lines, video showed. One protester climbed on top of a truck that was stopped at traffic lights.

Australian media reported it was the largest police operation in Melbourne since 2000 when Australia's second-largest city hosted the World Economic Forum.

About 1,000 exhibiting organisations from 31 countries are expected to attend the event through Friday, which the organisers said was Australia's largest defence expo.

Some attendees were doused in a red liquid by protesters, ABC News reported.

Prime Minister Anthony Albanese said people had the right to protest but had to do it in a peaceful manner.

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