Free speech demonstrators in San Francisco attacked by counter-protesters

Medics transport a supporter of Donald Trump to an ambulance after he was attacked by counter-protesters. Photo / AP

A free speech demonstration staged by conservative activists quickly fell apart in downtown San Francisco

today after several hundred counter-protesters surged the area, outnumbering and attacking those gathered, including knocking one in the mouth.

A photographer working for The Associated Press witnessed a Trump supporter being taken away in an ambulance and an injured San Francisco police officer on the ground by San Francisco's United Nations Plaza.

Team Save America organised the rally to protest against Twitter, which it said silences conservative speech. Members of the group wore red "Make America Great Again" Trump campaign hats and carried pro-police "Thin Blue Line" flags and US flags.

Philip Anderson, the organiser of the event, posted photos to social media of his bloody mouth with a front tooth missing and another hanging loosely. He said anti-fascist protesters attacked him "for no reason".

A tooth dangles from free speech rally organiser Philip Anderson's mouth after he was attacked by a counter-protester. Photo / AP

Anderson took the stage at about 1pm and was greeted by chants, plastic water bottles and glass bottles thrown over police barricades.

The event was cancelled, although both sides lingered in the area into the afternoon.

The San Francisco Police Department said three officers suffered non life-threatening injuries when they were assaulted with pepper spray and caustic chemicals. One officer was taken to a local hospital for treatment, the department said.

No arrests were made, the department said.

A counter-protester throws an egg at conservative activists. Photo / AP

Anderson called the counter-protesters hypocrites and said they are the reason why he's voting for President Donald Trump.

"I love America, I love this country and I love free speech," he said.