FERGUSON, United States (AFP) - US National Guard troops were deployed on Monday after unrest in a Missouri town where a white police officer shot dead an unarmed black teenager, as President Barack Obama called for calm.
A clearly uncomfortable Obama said there was no excuse for local police to employ "excessive force" and urged the state to make only "limited" use of the guards, while still condemning violent protest.
By late afternoon, about 200 National Guard soldiers arrived at command headquarters, with snipers posted on rooftops in the surrounding area. The troops are operating under Missouri Highway Patrol supervision.
The reinforcements allowed State Governor Jay Nixon to lift an overnight curfew, but tempers were still running high amid ongoing controversy over the death of 18-year-old Michael Brown.
"They're supposed to protect the American citizens, but they're fighting a war with unarmed citizens," said Ron Henry, who wore a t-shirt with the phrase "stop killing us."
Amid the trouble, Getty Images photographer Scott Olson was arrested for unknown reasons, the agency said.
As night fell, several hundred people took part in fresh protests after police with plastic handcuffs moved crowds of demonstrators into designated zones to clear a main street in the town that had been the scene of violent protests. Protesters were not allowed stop and gather, and were directed to keep moving.
Residents were on edge, after the previous night saw rioters loot stores and throw Molotov cocktails.
Shot six times
Brown was shot dead in broad daylight on a residential street on Saturday by Darren Wilson, a 28-year-old white police officer. A forensic pathologist retained by the victim's family revealed that the student had been shot six times - twice in the head.
Store surveillance footage released by local police appears to show Brown shoving an employee after snatching a box of cigars around half an hour before he was shot.
Different versions of the shooting have emerged, with police sources saying there was a scuffle during which Brown tried to seize the policeman's weapon, while witnesses have alleged that Brown had his hands up and was not resisting when he was shot.
The Washington Post said traces of marijuana were found in Brown's system. A total of three autopsies have been requested - by local authorities, the family and the Justice Department - due to the conflicting reports.
Officials told media that a Missouri grand jury could hear evidence in the case as early as Wednesday.
Beyond the shooting itself, many here were stunned by the police response to protests, deploying heavily-armed officers in army-style uniforms and military surplus armored personnel carriers. The dispute fueled resentment in Ferguson, a suburb of St Louis which has a majority African-American population but a mainly white police force - and now a detachment of National Guard soldiers.
"I'll be watching over the next several days to assess whether in fact, it's helping rather than hindering progress in Ferguson," Obama told reporters, referring to the National Guard deployment.
Attorney General Holder, who briefed Obama earlier, is due to travel to Ferguson on Wednesday to meet with FBI agents and Justice Department officials conducting a federal civil rights probe into the shooting.
On Monday alone, more than 40 FBI agents canvassed the neighborhood where Brown was shot, Holder said. He said a separate Justice Department autopsy was being performed by "one of the most experienced medical examiners in the United States military."
'Gulf of mistrust'
Obama also warned of a "gulf of mistrust" between residents and police in many cities and towns across America, particularly in those where racial minorities feel excluded from opportunities.
"To a community in Ferguson that is rightly hurting and looking for answers, let me call once again for us to seek some understanding rather than simply holler at each other," he said. "In too many communities, too many young men of color are left behind and seen only as objects of fear."
The president said the United States has taken strides in fighting centuries of the racial prejudice that many believe lay behind the August 9 police shooting, "but we have not made enough progress."
Former New York chief medical examiner Michael Baden, who examined Brown's body on behalf of his family, said he found no evidence of an alleged struggle between Brown and the officer.
Wilson is said to have been hurt in the incident, and Baden said that he had not examined Wilson. The absence of gunpowder on Brown's body indicated that the muzzle of the gun was probably at least a foot or two - or as much as 30 feet (10 metres) - away, Baden added. He stressed that his findings were preliminary.