61 people arrested in Ferguson

Angry crowds set fire to buildings and cars and looted businesses with police responding with tear gas.

Firemen stand outside a burnt-out laundromat after protesters burned buildings in protest against the Grand Jury decision not to indict a police officer in the shooting death of Michael Brown, in Ferguson, Missouri, USA, 25 November 2014. Picture: EPA.

JOHANNESBURG - An estimated 61 people have been arrested in the United States (US) following hours of violence in Ferguson, Missouri, triggered by a grand jury's decision not to charge a white policeman for killing an unarmed black teenager.

Michael Brown was gunned down in August in what officer Darren Wilson claims was an act of self-defence.

Shortly after the jury announced its decision, angry crowds set fire to buildings and cars and looted businesses with police responding with tear gas.

Demonstrators began clashing with police soon after the jury's announcement was made by the prosecutor late last night.

The clashes have continued until the early hours of the morning.

Buildings have been set on fire and there were reports of heavy automatic gunfire as well as looting of stores.

The anger and dismay has spread far beyond the borders of the St. Louis suburb.

Crowds marched in New York, Los Angeles and Seattle and are expected to do so again as the new day begins.

Prosecutors have released photos and documents pertaining to the decision to clear the police officer.

Supporters of Brown's family backed witness accounts that Wilson fired while Brown had his hands up in surrender.

TWO SIDES OF TRAGEDY

Wilson could have faced charges ranging from involuntary manslaughter to first-degree murder, and Brown's family said through their lawyers that they were "profoundly disappointed" by the grand jury's finding.

"While we understand that many others share our pain, we ask that you channel your frustration in ways that will make a positive change," the family said in a statement.

Attorneys for Wilson, who was placed on administrative leave and has avoided the spotlight since the shooting, said he was following his training and the law when he shot Brown.

"We recognise that many people will want to second-guess the grand jury's decision. We would encourage anyone who wants to express an opinion do so in a respectful and peaceful manner," the statement said.

As unrest flared following the announcement of the decision, Barack Obama called for protesters to remain peaceful and for police to show restraint.

"We need to recognise that the situation in Ferguson speaks to broader challenges that we still face as a nation," the president told a televised news conference. "In too many parts of this country a deep distrust exists between police and communities of colour."

As protests escalated in Ferguson, a group mobbed a police car, throwing rocks and knocking out its windows, prompting a group of officers in riot gear to advance. Sounds of gunshots briefly caused police to take cover behind their vehicles.

Missouri Governor Jay Nixon called up the National Guard ahead of the ruling to protect against the kind of rioting that erupted in the weeks after Brown was shot and killed.

Some activists criticized the pre-emptive deployment as unnecessarily heavy-handed, particularly following complaints that police inflamed crowds in August by responding with tear gas and rubber bullets.

But Belmar said thousands of officers would have been needed to contain the unrest that swept the Midwestern town on Monday night.

Additional reporting by Reuters