FERGUSON: Tensions rose Saturday in the troubled St Louis suburb of Ferguson, with a grand jury poised to decide whether to prosecute a white police officer for killing an unarmed black teenager.

US President Barack Obama has called for calm, Missouri’s governor declared a state of emergency and activated the state National Guard, and the FBI has deployed an extra 100 personnel in the city.

Police helicopters trained search lights over Ferguson late Friday as a small gaggle of protesters braved the cold to demand officer Darren Wilson stand trial for shooting 18-year-old Michael Brown on August 9.

Brown’s killing led to weeks of violence that inflamed racial tensions in the St Louis suburb of 21,000, which has an African American majority and an overwhelmingly white police force and town government.

“I’m here for justice. If we don’t get justice, aint nobody gonna get no peace,” said 22-year-old Ebony, who works in security and refused to give a second name.

“We’re going to keep protesting until we know what’s right gets done,” she told AFP late Friday. “I want to see Darren Wilson go to jail.”

Brown, a high-school graduate planning on attending technical college, was shot at least six times by Wilson. His body was left in the street for hours.

Wilson reportedly told the grand jury he acted in self-defence after tussling with the youth. Others claim Brown had his hands up in the air when he was shot.

A father of two, protesting overnight with his face hidden behind a Halloween mask, said tensions were rising in the suburb.

“I think there’s going to be some angry people, that’s all I know,” said the man, who refused to give his name.

In the United States, grand juries meet in secret to review some cases before deciding whether criminal charges should be brought.

The jury could indict Wilson, meaning he could face trial, or it could determine there is no case for him to answer.

Few of the protestors believe the jury will indict Wilson.

“It’s not going to be pretty if it’s not a verdict. There’s going to be violence, I do believe,” said Jo Ann Davis, a government employee.

“I think it’s going to be worse than it was back in August. Because you’ve got busloads of people that came in here from all over the world just to protest.”

Cathy Jackson, a grandmother of four, said people were apprehensive.

“I think everybody’s kind of anxious, a little nervous about what’s going to happen,” she said. “I think the police are just amped up way too much.”

“I don’t want to say they’re going to riot, loot and all of that. I know we’re going to keep protesting until something changes... racial profiling, that’s the main thing. That has got to stop.”

On Friday, two suspected members of the new Black Panthers were arraigned in a federal court after being arrested by the FBI.

“First and foremost, keep protests peaceful,” Obama said Friday.

“This is a country that allows everybody to express their views, allows them to peacefully assemble to protest actions that they think are unjust, but using any event as an excuse for violence is contrary to rule of law and contrary to who we are.”

Brown’s father, Michael Brown Sr, also appealed for restraint. “Hurting others or destroying property is not the answer,” he said in a somber video plea.

St Louis County prosecutors have said they are setting up a press conference to announce the decision, but have not confirmed the date, time and location.

Schools in the area announced they would close Monday and Tuesday due to potential unrest. The Thanksgiving holiday will keep them closed for the rest of next week.

Some demonstrators in August complained that police used undue force during peaceful protests. There was widespread criticism of military-style weapons and protective gear deployed by local officers.