Chaos engulfed downtown Melbourne on Wednesday as anti-Israel demonstrators clashed with Australian police outside a major defense industry exhibition.

Organized by Students for Palestine and Disrupt Wars groups, thousands descended onto Melbourne’s Convention Center to protest Israel’s “genocide” in Gaza. In what local media described as the most significant show of force since the 2000 World Economic Forum, about 1,800 police officers were sent to protect the 31 country international delegation attending the International Land Defense Exposition.

Viral footage from the scene shows numerous protesters waving PLO flags and chanting anti-Israel slogans through loudspeakers.

“From the river to the sea, Palestine will be free,” an antisemitic chant calling for the anihilation of Israel, was heard repeatedly during the protest. Protesters are seen hurling rocks, acid, and excrement at officers as they tried to break the barricades.

“Victoria police is appalled at the behavior of some of the protesters in attendance. If you wish to come and protest, do so peacefully. We will not tolerate criminal behavior,” a Victoria state police spokesperson said in a statement. “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.”

According to ABC7, 24 officers required medical attention, and 39 individuals were arrested on charges including assaulting police, arson, and obstructing roads.