Hundreds of people blocked the busy Flinders Street intersection on Saturday night in support of an anti-racism campaigner who was pepper-sprayed by police on Friday.

Uganda-born Jafri Katagar returned to the tram stop in front of the Young & Jackson pub where he regularly stands with a sign reading "Stop Racism Now".

About 4.30pm on Friday, Mr Katagar was sprayed in the face after police asked him to move. Police said they had received "reports of a number of near misses between passing traffic and a protester standing in the middle of the street".

Hundreds of protesters converged at the intersection on Saturday in a show of support for Mr Katagar and to demand accountability from Victoria Police.

Supporters chanted "apologise, apologise" as police officers watched on.

Dilmen Ramadan, who had filmed Mr Katagar being sprayed, told the rally that the officer responsible should be "sacked".

"Surely, three trained police officers could have handled one unarmed peaceful protester without resorting to pepper spray," she said.

Mr Katagar told The Age that the police who detained him later told him he was not under arrest.

"I don't know whether they're going to lay any charges, but if they (lay charges) of course I have lawyers," he said.

"I was pepper-sprayed directly onto my eyes; heavy pepper spray onto my eyes, my face, my neck, my arms.

"I couldn't see, it was really burning me so hard.

"The police spent almost an hour pouring water on my face until I started feeling better and that's when they released me."

Mr Katagar said the experience hadn't "killed" his spirit.

"Someone like me, I have a beautiful heart. I love all people and want us to unite together as one people.

"I shouldn't be harassed by the police; I shouldn't be detained by the police.

"But I'm going to keep fighting against racism."