Demonstrations from New York to Seattle were mostly peaceful, with protesters chanting and waving placards.

In and around the St Louis suburb of Ferguson, scene of major riots on Monday, 2,200 National Guard troops were deployed to stop further unrest.

The white officer who killed Mr Brown there says he has a "clean conscience".

Darren Wilson shot the 18-year-old on 9 August, sparking weeks of unrest in the Missouri town.

Many in Ferguson's predominantly African-American community had called for the officer to be charged with murder, but the grand jury's decision means the police officer will not face state criminal charges over the shooting.

Lawyers for Mr Brown's family have denounced the grand jury's decision as "unfair".

'Black lives matter'

With the number of troops more than trebled, the situation in Ferguson was calm for most of Tuesday, though demonstrators briefly closed a major road in central St Louis and rallies were staged outside the federal court house.

Late in the evening, however, tension began to rise. Protesters set a police vehicle alight after failing to overturn it, and police began to clear streets, making a number of arrests.

There's been confrontation outside Ferguson City Hall where a police vehicle was burnt earlier and tear gas still hangs in the air. There's a heavy police presence with several armoured cars and vehicles.

There is tension as police try to move people from the area - officers are saying anyone standing in the street will be subject to arrest. Some are giving chase to people in the surrounding streets and tonight they have dogs with them. A police helicopter is hovering overhead with a spotlight.

Further along, police and the National Guard face off with an angry crowd in front of the Police Department. There are fewer protesters, but a larger media presence. The crowd is jittery and there is a sense there could be further clashes.

(BBC News)