A man has been arrested after driving his motorcycle through a crowd of anti-Trump protesters in San Francisco

Dozens of activists were staging a 'die-in' against President Donald Trump's healthcare plans by lying in the middle of the road outside the San Francisco Federal Building.

In video of the incident, protesters can be seen lying or standing on the road with signs before a red motorcycle begins to drive up behind them.

Though it was only moving slowly, the motorcycle was being revved loudly and caused concern among the activists yesterday afternoon.

Pictured: The horrifying moment the motorcyclist drove through the protesters in San Francisco

The demonstration, a 'die-in', had been organised by Bay Resistance and Senior and Disability Action. Pictured: The motorcyclist comes closer as he revs his engine

Pictured: The porotester's concern is obvious as the man drives his red bike between the crowd

Police arrested the man (pictured) after - according to one witness - ordering to stop with a drawn gun

Many of the protesters were elderly or using wheelchairs since it was organised by Bay Resistance and Senior and Disability Action.

A spokeswoman for Bay Resistance, Emily Lee, said the driver was 'definitely targeting us', according to CBS.

She added: 'Everyone thought he was just confused, but he didn't stop, and at some point it became clear he was going to come through the crowd and people jumped out of the way.'

Lee added that the man then turned around and began driving back into the activists before a police officer drew his gun and ordered him to stop.

The protesters were outside the San Francisco Federal Building to express their anger at President Trump's plans to change healthcare. Pictured: Activists holding signs

Pictured: A sign held high during the protest in San Francisco

Pictured: The motorcyclist being arrested by police

One man (pictured right) ran after the motorcyclist and attempted to stop him

The man is being held in custody but no charges have yet been made.

No injuries have been reported after the incident.

Republicans have been working for weeks on legislation aimed at repealing and replacing major portions of the Affordable Care Act, former Democratic President Barack Obama's signature healthcare law, popularly known as Obamacare.

It was one of President Trump's central pledges during the election campaign.

An estimated 23 million people could lose their healthcare under the House plan, according to the non-partisan Congressional Budget Office.