A police car was set on fire outside the Ferguson city hall on Tuesday night. News agency AP reports the car appeared to have been set on fire by a group of people who had broken off from a crowd of mainly peaceful demonstrators.

It comes after the Missouri governor, Jay Nixon, ordered more than 2,000 National Guard troops on Tuesday into Ferguson, a suburb of St Louis. It follows a night of violence over a grand jury's decision not to indict the white police officer who shot and killed unarmed black teenager Michael Brown in August.

The verdict was met with anger in the predominantly black community, which is patrolled by a predominantly white police force. Riots, looting and arson broke out, with the destruction of a number of buildings and several businesses burned and looted. Dozens of people were arrested.

Brown's family have condemned the decision, labeling the US criminal justice system "broken." The verdict also sparked protests in other US cities, such as New York (seen above), though without any major disturbances.

Police officer speaks

The officer who shot Brown, Darren Wilson, has defended his actions in his first public statement since the shooting. Wilson told ABC News he had a clear conscience, as he felt he could not have done anything differently in the confrontation with Brown.

"The reason I have a clean conscience is because I know I did my job right," Wilson, 28, said.

"I don't think it's haunting. It's always going to be something that happened." He said the situation would have ended in the same way had Brown been white, as he feared for his life and acted out of self defense.

"I gave myself another mental check. Can I shoot this guy? Legally, can I? And the question that I answered to myself was, 'I have to.'"

Wilson's side of the story was already known because of his testimony to the grand jury, released shortly after the verdict.

"I felt like a 5-year-old holding on to Hulk Hogan," he said as he described a struggle with Brown from inside his police car.

Brown's death reignited a nationwide debate and highlighted long-standing tensions over race relations, police tactics and the use of firearms.

Obama says he understands frustrations

White House officials are still deciding whether US President Barack Obama should travel to Ferguson. In comments on Tuesday, Obama deplored the violence, saying offenders should be prosecuted, but said he understood why so many people were upset.

"The frustrations that we've seen are not about a particular incident. They have deep roots in many communities of color who have a sense that our laws are not always being enforced uniformly or fairly," Obama said.

DW's Washington correspondent, Richard Walker, says Obama's approach has changed.

"The emphasis of what he said today was actually quite different. He really quite reached out to the protesters. He stressed that the frustrations...are felt in communities like Ferguson and many parts of the country...

"He said that that perception was not made up, that it was rooted in reality in many parts of the country and he appealed to protesters to be constructive, to try and help change that and that if they do that, he will be on their side."

jr/jm (AP, AFP, Reuters)