FERGUSON: Gunshots were heard and bottles were thrown as anger rippled through a crowd outside the Ferguson Police Department in suburban St Louis after authorities on Monday announced that a grand jury voted not to indict a white officer in the August shooting death of an unarmed black teen.

Whistles pierced the air as some of the hundreds of protesters tried to keep the peace, shouting, “Don't run, don't run.”

Police who formed a wall of clear riot shields outside the precinct were pelted with bottles and cans as the crowd surged up and down the street immediately after authorities said the grand jury voted to not indict Officer Darren Wilson in the shooting death of 18-year-old Michael Brown.

“Murderers, you're nothing but murderers,” the crowd shouted. One woman, speaking through a megaphone said, “Stinking murderers.” Not far from the stretch of Ferguson that saw the worst of the rioting after Brown's fatal shooting in August, dozens of police and military vehicles were poised for possible mass arrests.

“They need to feel the pain these mothers feel at the (expletive) cemetery,” shouted Paulette Wilkes, 40, a teacher's assistant who was in the crowd at the police department.

A smaller, calmer crowd of about three dozen protesters gathered outside the courthouse where the grand jury had met, including one white woman holding a sign reading, “Black Lives Matter.” Many of the protesters looked stunned.

“That's just how the justice system works — the rich are up there and the poor are down here,” said Antonio Burns, 25, who is black and lives in the Ferguson area. The police “think they can get away with it.”

A handful of Amnesty International volunteers in bright vests tried to maintain the peace. Brown's family immediately urged a non-violent response to the grand jury's decision.

Officials urged tolerance and assured residents that the National Guard would provide security at critical facilities like fire houses, police stations and utility substations.

“I do not want people in this community to think they have to barricade their doors and take up arms,” St. Louis County Executive Director Charlie Dooley said ahead of the announcement of the decision.

Elsewhere in the United States, protesters gathered in mostly peaceful demonstrations. In New York, protesters massed in the streets of Times Square, shouting and pounding drums.

In Chicago, dozens of protesters gathered outside police headquarters, sang protest songs, called out the names of black people killed by the Chicago police, read statements and poems and chanted, “Hey, ho, these killer cops have got to go.”

Missouri police officer not charged in black teen's shooting

A Missouri grand jury voted not to charge a white police officer for the fatal August shooting of an unarmed black teenager, an incident that set off weeks of sometimes violent protests around the St Louis area, a county prosecutor said on Monday.

The grand jury found there was no probable cause to charge Ferguson, Missouri, police officer Darren Wilson with any crime for the shooting of 18-year-old Michael Brown, an incident that highlighted longstanding racial tensions in the predominantly black city, which has a white-dominated power structure.

“They determined that no probable cause exists to file any charge against officer Wilson,” St Louis County Prosecutor Bob McCulloch told reporters in Clayton, Missouri, a suburb of St Louis where the grand jury met. Brown's family said they were “profoundly disappointed” by the grand jury's finding.

“While we understand that many others share our pain, we ask that you channel your frustration in ways that will make a positive change,” the family said in a statement released by its attorneys.

Some activists described the decision to preemptively activate the guard as unnecessarily heavy-handed, particularly following complaints that police inflamed crowds in August by responding in a heavily militarised posture, using tear gas and rubber bullets.

Ahead of the decision, officials called on area residents to remain calm following the grand jury's decision.

The grand jury, with nine white and three black members, began meeting in late August and heard evidence that included witnesses called by the prosecution as well as a private pathologist hired by the Brown family to review the shooting. Nine jurors needed to agree to bring charges.

McCulloch declined to say if the jury's decision was unanimous, noting that grand jury proceedings are completely secret and that only the jury members themselves know the details of the proceedings.

Obama urges calm after Ferguson decision

US President Barack Obama urged the people of Ferguson, Missouri, on Monday to react peacefully to a grand jury's decision not to indict a white policeman in the fatal shooting of an unarmed black teen, and for police to show restraint.

Obama spoke in the White House briefing room shortly after a county prosecutor announced the grand jury's decision regarding the August 9 shooting that set off weeks of sometimes violent protests in the St. Louis suburb and highlighted racial tensions in the community.

The president said the people of Ferguson needed to accept that it was the grand jury's decision to make and that they should channel their concerns constructively.

US issues flight restrictions over Ferguson

The Federal Aviation Administration is restricting the path of some flights into Lambert-St Louis International Airport amid the unrest in Ferguson following a grand jury's decision not to indict the white police officer who fatally shot a black 18-year-old.

According to an advisory posted late Monday, planes were being rerouted out of an at least 3-mile (4.8-kilometre) area near Ferguson.

The reason cited was “to provide a safe environment for law enforcement activities.” An FAA spokesman didn't immediately return a call from The Associated Press.

The airport posted on Twitter that only inbound planes, not departures, are affected. The facility remains open.

For two weeks after the August shooting, the FAA restricted flights on 37 square miles (95 sq. kilometres) of airspace, including for news helicopters.