Winnipeg police have arrested a man who was taking part in the Take Back Canada rally in the city's downtown.

Police confirmed that a 20-year-old man was taken into custody during the rally and march, which began late Monday afternoon at the Manitoba legislature.

At one point, the man was taken to the Health Sciences Centre for a medical issue, said police, although they would not elaborate on what that issue was.

Video footage captured by other protesters show police officers and an ambulance at the scene.

Police say the man was later transported from hospital to a police station, where he is facing charges of assaulting a peace officer and obstructing a peace officer.

Almost 100 people attended the rally, which protested the federal Conservative government and recent measures such as the omnibus crime bill.

The rally also took place on the one-year anniversary of the Occupy movement that produced protests around the world last year.

'Shock and terror'

Protester Damon Bath said it was a shock when so many police officers pulled up beside the marchers, who had left the legislature and were walking near Portage Place Mall downtown.

"It happened within seconds. The police, 12 cars came up beside us," Bath told CBC News on Tuesday.

"It was more of a feeling of shock and terror."

Video posted online by someone filming the march shows numerous officers surrounding a man against one of the cruiser cars.

Protesters can be heard demanding he be let go, or asking police for an explanation for the arrest.

Then the man can be seen lying on the ground, legs kicking and arms flailing, and the shouts from the protesters become more urgent.

Officers form a defensive circle between the man and the rest of the crowd until an ambulance arrives about five minutes later.

Police deny Taser claims

There is no word on the man's condition.

Following the incident, there were several rumours and tweets on social media sites that the man had been shocked by a Taser stun gun, but police say no Taser was discharged.

On Tuesday, police said they initially stopped the protesters to find out where they were going because they didn't have a permit.

The protesters were also marching on busy Portage Avenue, and police wanted to get the crowd off the street.

Officers asked who was leading the group but were told there were no leaders. They then were confronted by some protesters and detained one.

When that happened, the officers were swarmed and then shoved by another man — the 20-year-old now facing charges.

A total of 17 Take Back Canada protests took place across the country on Monday.