People protesting against the Ferguson jury decision took to the streets in some US cities for a second day, even as others were still cleaning up vandalism from the night before.
Protesters on Tuesday disrupted traffic for several hours in central St Louis by blocking major intersections, an interstate highway and a Mississippi River bridge connecting the city to Illinois.
Riot police arrested at least 40 protesters including several who sat in the middle of an interstate highway. They used pepper spray to disperse the crowd.
People are calling for justice after the grand jury ruled not to indict a white police officer who killed an unarmed black teenager, Michael Brown.
Al Jazeera's Daniel Lak, reporting from Ferguson, said that National Guard soldiers stepped in to assist police with controlling the crowd.
"Some protesters were arrested outside the Ferguson Police Department after someone in the crowd threw what appeared to be a water bottle at the lines of police and National Guard soldiers," our correspondent said.
"Three armoured vehicles moved in and soldiers joined the police for the first time tonight, shouting at people to move back. National Guard troops pinned protestors on the ground and a number were put in the back of a police armoured vehicle."
There are a few hundred protesters in the streets, shouting, chanting slogans, but nothing quite like last night. At least up until now.
This place, near the Ferguson Police Department, was where it all went bad last night, with tear gas, fusillades of bottles, stones and batteries thrown at police.
A few things were thrown tonight but there are extra police and national guardsmen here at the scene.
The mood tonight is slightly tense but there are a lot less people in the streets, maybe because it's very cold.
Elsewhere, police said protesters briefly shut down the Brooklyn Bridge and one of the three spans of the Robert F Kennedy Bridge, formerly known as the Triborough Bridge.
More than a thousand people took to the streets in the nation's capital. Rallies were also held on Tuesday in Newark, New Jersey, Portland, Maine, Baltimore and elsewhere.
"Mike Brown is an emblem (of a movement). This country is at its boiling point," said Ethan Jury, a protester in Philadelphia, where hundreds marched. "How many people need to die? How many black people need to die?" Jury added.
Earlier in the day, Missouri governor, Jay Nixon, ordered more than 2,200 National Guardsmen troops to the region near Ferguson rocked by rioting.
Meanwhile, in his first public statements during an interview with ABC News, white police officer Darren Wilson said he has a clean conscience because "I know I did my job right".
President Barack Obama condemned the violence, saying they are criminal and those responsible should be prosecuted.
But America's first black president said he understands that many people are upset by the grand jury decision. He said that their frustration is rooted in a sense that laws are not always being enforced "uniformly and fairly" in communities of colour.
"Burning buildings, torching cars, destroying property, putting people at risk ... there's no excuse for it," Obama said.Obama urged parties aggrieved by events in Ferguson to work peacefully to achieve change, saying the case had exposed "an American problem".
Lawyers for Michael Brown's family said the process that led to the white officer not being indicted was "unfair and broken".
Benjamin Crump said on Tuesday that the family's legal team objected to St Louis County Prosecutor Bob McCullough's decision to call a grand jury in the case and not appoint a special prosecutor.
Speaking at a news conference in Ferguson, where Brown was shot on August 9, Crump also called for protests to remain peaceful.
Source: Al Jazeera and agencies