Ferguson (United States) (AFP) - The midwestern US town of Ferguson was recovering from another night of violence on Tuesday as a police crackdown on protests against the killing of an unarmed black teenager continued.
In the past ten days, this mainly black suburb of St Louis, Missouri has become a global symbol of the tensions created by the United States' racial divide and heavy-handed law enforcement tactics.
Overnight, protesters shot at police and threw rocks and firebombs in a new spasm of violence that left six wounded and led to 31 arrests.
Police responded with tear gas to disperse the crowd of about 200 in the town, Captain Ron Johnson of the Missouri Highway Patrol said.
Johnson said two demonstrators and four officers were injured, and argued that police had showed restraint by not opening fire.
On August 9, 18-year-old Michael Brown was killed in broad daylight on a residential street by Darren Wilson, a 28-year-old white police officer -- triggering a wave of community protests.
Although police have since fingered Brown as a robbery suspect, he was unarmed at the time of shooting and some witnesses have said he was surrendering when he was hit six times, twice in head.
Monday's demonstration started peacefully, only hours after President Barack Obama, made a televised appeal for calm.
But, according to Johnson, a loud group of about 200 moved toward the police and a small minority among them attacked officers in riot gear.
"There is a dangerous dynamic in the night," Johnson said. "It allows a small number of violent agitators to hide in the crowd and then attempt to create chaos."
He added: "Our officers came under heavy gunfire."
Johnson stood behind a table on which a gun and a Molotov cocktail he said had been seized from protesters were on display.
Some of those in the crowd were not locals but rather people from as far away as New York and California, he said. The news conference began with a prayer for peace led by a county chaplain.
"Protesters are peaceful and respectful. Protesters don’t clash with police," Johnson said. "It is criminals who throw Molotov cocktails and fire shots that endanger lives and property."
US National Guard troops had rolled into Ferguson earlier in the day, but they kept a low profile as police in riot gear dispersed the demonstrators around 11:00 pm (0400 GMT).
Obama, the nation's first African-American president, said Attorney General Eric Holder would arrive in Ferguson on Wednesday to oversee a federal civil rights investigation into the case.
Obama said there was no excuse for local police to use "excessive force" and urged Missouri to make only "limited" use of the National Guard, which is operating under police supervision.
- 'Gulf of mistrust' -
The Guard reinforcements allowed State Governor Jay Nixon to lift an overnight curfew, but tempers were still running high.
"They're supposed to protect the American citizens, but they're fighting a war with unarmed citizens," said demonstrator Ron Henry, who wore a T-shirt emblazoned with the words "Stop Killing Us."
A forensic pathologist retained by Brown's family revealed that the student had been shot at least six times -- twice in the head.
A total of three autopsies have been requested -- by local authorities, the family and the Justice Department.
Officials told news media that a Missouri grand jury could hear evidence in the case as early as Wednesday.
Obama 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 for a better life.
"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.