Media playback is unsupported on your device Media caption The BBC's Aleem Maqbool reports on the tension between Ferguson's majority black population and overwhelmingly white police force

Police in the US state of Missouri have clashed with protesters for a fourth night amid growing anger at the fatal shooting of a black teenager by police.

Heavily armed riot police fired tear gas as they moved in on demonstrators in the St Louis suburb of Ferguson who had ignored an order to disperse.

Several people were arrested, two of them journalists who said they were assaulted before being released.

The tension was sparked by the death of Michael Brown, 18, on Saturday.

Details about the incident have been disputed but eyewitnesses said the unarmed teenager had his arms raised when he was shot multiple times by a police officer.

Police say there was a struggle and the officer suffered facial injuries.

Image copyright Reuters Image caption Heavily armed riot police moved in to disperse protesters after they ignored a plea to return to their homes

Image copyright Getty Images

Image copyright Getty Images Image caption Tear gas was used to disperse protesters

Image copyright Getty Images Image caption Some protesters were seen throwing Molotov cocktails at the police

Racial disparity

As the outrage showed no sign of dissipating, Missouri Governor Jay Nixon said he would travel to the area on Thursday and called for "patience and calm" from members of the community.

"While we all respect the solemn responsibility of our law enforcement officers to protect the public, we must also safeguard the rights of Missourians to peaceably assemble and the rights of the press to report on matters of public concern," he wrote in a statement.

"I am committed to ensuring the pain of last weekend's tragedy does not continue to be compounded by this ongoing crisis."

At the scene - Aleem Maqbool, BBC News, Ferguson

Of those young black men and women taking to the streets, many say they have no other outlet to show their objection - not just to the way Michael Brown died, but to the way the police treats them as a community - and that they will not stop protesting until they are listened to.

While demonstrations throughout have been vociferous, for the most part they have been peaceful. They were again during the day on Wednesday. But after dark, police seemed intent on enforcing what had earlier been a request that "all those wishing to demonstrate, disperse well before the evening hours".

Tear gas was used and police lines swept through roads in the suburb of Ferguson that have been the focus of the confrontations.

Requests for calm have come even from the White House, but there is a sense that the young people on the streets have the moral support of many among the older generations within their community here, who also see this as an opportunity for long overdue change.

The killing and the resulting protests have laid bare tension between Ferguson's majority black population and its overwhelmingly white police department, analysts say.

The town's population of 21,000 is two-thirds black, while only three of the local police force's 53 officers are black.

Ferguson Police Chief Thomas Jackson has said his priority was improving race relations in the town.

On Wednesday, the Ferguson police department asked protesters to gather only in the daylight and to disperse "well before the evening hours" for safety reasons.

The plea came after three nights of tense, sometimes violent protests that resulted in dozens of arrests, looting and the burning of a shop.

Despite this appeal to stay away, and calls for calm from President Barack Obama, Mr Brown's parents and civil rights activist the Reverend Al Sharpton, the anger seemed as palpable as ever on the streets of Ferguson on Wednesday night.

Image copyright Getty Images Image caption A TV camera crew were forced to run for cover after police fired tear gas close to where they were filming

Image copyright Other - Facebook Image caption Michael Brown had recently graduated from high school

Tear gas

Armoured vehicles blocked off streets and protesters linked arms defiantly as they were told through loudspeakers to leave the area or face arrest.

The demonstrators chanted: "Hands up, don't shoot."

Molotov cocktails were thrown at lines of police, who launched smoke bombs and fired tear gas.

Two journalists were briefly detained by police earlier on Wednesday while working inside a McDonald's restaurant.

One of them, Ryan Reilly of the Huffington Post, told BBC Outside Source an officer handcuffed him, applied force to his neck, and "purposefully" banged his head against a glass window and then "sarcastically apologised".

He and Welsey Lowery of the Washington Post were taken to the police station but soon released, apparently after a third reporter called the Ferguson police chief and asked for comment.

"The only reason we're out is because of the fact that we are reporters," Reilly said. "If they treated a white reporter who was working on his laptop that way, I can't imagine how terribly they're treating other people."

Lowery later tweeted: "Apparently, in America, in 2014, police can manhandle you, take you into custody, put you in cell & then open the door like it didn't happen."

Media playback is unsupported on your device Media caption Freelance Journalist Mariah Stewart: "The protesters want to see change"

Civil rights activists and Mr Brown's family and friends have called for an end to the clashes, while also demanding that police release the name of the officer who shot and killed Mr Brown.

The authorities have declined to release the name, citing concerns for his safety, a decision that has been criticised by protesters demanding more transparency.

The officer has been placed on administrative leave.

President Obama has promised a full investigation by the US Department of Justice into the teenager's death, and the FBI has launched its own inquiry.