A Trump supporter was arrested after spraying bear repellent on a crowd protesting against the president at Santa Monica Pier, authorities said.

Pro and anti-Trump demonstrators began shouting at each other on Saturday when a scuffle broke out, Santa Monica police said.

A video posted online showed a man wearing a red 'Make America Great Again' hat circling the crowd and then unleashing a torrent of spray from a canister.

Some in the crowd were seen holding Donald Trump and US flags, while others waved orange posters that read 'Trump Pence Must Go'.

Both groups appeared to be involved in an argument before the the substance was sprayed at the panicked crowd.

Supporters of President Donald Trump (left) clash with anti-Trump protesters during a rally against his policies in Santa Monica before bear repellent was sprayed by a man in a MAGA hat

Two men scuffled on the floor during anti and pro-Trump demonstrations on Santa Monica Pier

Before the violence erupted, one man could be heard chanting 'Trump 2020'.

Nobody was seriously hurt by the repellent, which is similar to pepper sprays used by police, officials said.

Many ran away screaming and coughing and one woman was seen vomiting nearby the scene at around 1.20pm, a witness told KTLA 5.

The man could be seen pulling a canister from a holster and using it on the crowd during the brawl, pointing the can in various directions.

Police soon arrived and cornered the man, who protested his innocence, as enraged protesters told officers he had a weapon.

He was then led away in handcuffs to cheers from the anti-Trump demonstrators.

One man who bore the brunt of the spray, speaking to a camera, said he poured milk on his face to counteract the effects of the substance.

A supporter of President Trump being handcuffed and arrested after a clash with anti-Trump protesters as a rally turned violent

Police help a pepper spray victim after supporters of President Trump sprayed the crowd during a clash with anti-Trump protesters

Anti-Trump protesters chanting during a rally against his policies moments before a violent clash with supporters of the president that saw some members of the crowd pepper sprayed

A man who could face charges including violating the terms of his parole from a previous weapons violation, according to the Los Angeles Times.

His name was not released and investigators are trying to determine whether a second man also sprayed the crowd.

Atlas Winfrey, an organizer of the anti-Trump demonstration, told local media: 'The Trump supporters were already there on the Pier when we got up there from the beach.

'The Trump people wearing their MAGA hats and waving flags were there to intimidate and incite a confrontation.''

The protest was organized by the group RefuseFascism.org and coincided with other protests held across the country on Saturday, including New York City.

Anti-Trump protesters holding an 'impeach' sign during a rally against his policies before a violent clash with supporters of President Trump in Santa Monica