A trans-exclusionary women’s rights rally has been ambushed by pro-trans protestors in Melbourne CBD.

The Women Will Speak rally formed on the steps of Parliament House on Spring St with a heavy police presence about 11.30am on Saturday.

Crowds cheered as speakers told the crowd that “humans cannot change sex” and asserted beliefs that women are being “dehumanised as cervix-havers” and will be wrongly persecuted under new hate speech laws.

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About 120 people attended the rally, where protestors held up signs for “sex-based rights”.

Several large signs also spotlighted the controversial concept of autogynephilia — a stigmatised term commonly used to posit trans gender identity as a fetish — reading: “Look it up without being sick”.

But before the rally was well underway, an opposing march of about 80 pro-transgender activists marched up from Carlton Gardens.

They called the Women Will Speak rally transphobic and fascist.

Footage shows masked protestors dressed all in black clashing violently with police.

Four people were arrested by Victoria Police who said their “top priority was keeping the peace and ensuring the safety of those attending and the broader community.”

Pepper spray was used on a 21-year-old Flemington man who was arrested after he allegedly struck a police officer with an umbrella at the intersection of Russell St and Lonsdale St just before 11.30am.

He was charged with assault police and bailed to appear at court at a later date.

A 19-year-old Wallington woman and a 27-year-old man from Coburg were arrested after allegedly being in possession of flares, and both are expected to be charged on summons.

A 33-year-old Oakleigh South man was arrested for failing to move on and is also expected to be charged on summons.

A group of neo-Nazis had also reportedly claimed that they would ambush the rally, according to the Herald Sun.

Police conducted about 145 searches, and gave 50 orders to remove face coverings.

“Officers did not locate any weapons,” police said.

The strong police presence, including general duties officer, the Public Order Response Team, and the Mounted Branch and Highway Patrol.

“Victoria Police respects the right for peaceful protest however will not tolerate unlawful behaviour,” police said.