Thousands of protesters have marched through St Louis, Missouri, as part of a weekend of demonstrations against police violence organised after the fatal shooting of an unarmed black teenager by a white officer last summer.

Organisers of Saturday's march included Hands Up Unite, an activist group that emerged after the August 9 shooting of unarmed 18-year-old Michael Brown in suburban Ferguson, Missouri.

Civil rights organisations and protest groups have invited people from around the country to join vigils and marches in the St Louis area from Friday to Monday.

Tory Russell, one of the founders of Hands Up United, pledged to keep up the pressure on police to change how they deal with young black men.

He said he expected the grass-roots movement that sprang from the Ferguson shooting to pick-up momentum.

The weekend got off to a tense but peaceful start on Friday night, a break from the clashes with police that have erupted in the area in recent days.

Police said there had been no arrests, injuries or damage from the night's protests.

The Saturday afternoon rally was joined by union members, gay rights activists and people from the Occupy movement.

There were even supporters of the Palestine cause carrying placards reading "#Palestine2Ferguson".

Four days of events are planned.

On Friday, afternoon protesters marched outside the St Louis County prosecutor's office in Clayton and renewed calls for prosecutor Bob McCulloch to charge Darren Wilson, a white officer, over the shooting of Brown.

Wilson remains free and on administrative leave while a St Louis County grand jury weighs whether Wilson should face criminal charges. 

The US Department of Justice has opened a civil rights investigation of Brown's shooting which led to a nationwide dialogue about interactions between minorities and police.

Source: Agencies