Video has emerged of protesters in St Louis running in fear as they are chased after by police officers firing projectiles into the crowd. It is not clear what projectiles the police were using.

Video posted by Jon Ziegler, a digital journalist who goes by the name “Rebelutionary_Z,” shows a crowd marching through the Missouri city at night.

As the crowd approaches an intersection, a few people begin to yell in alarm. The protesters flee from the intersection, and police can be seen chasing after them.

“They’re spraying rubber bullets,” someone says.

Another voice can be heard yelling: “Get down!”

Ferguson Anniversary Protests Show all 11 1 /11 Ferguson Anniversary Protests Ferguson Anniversary Protests Ferguson Anniversary Protests Police take a mug shot of a protester who was detained in Ferguson, Missouri, August 10, 2015. Protesters regrouped in Ferguson, Missouri, on Monday evening after a state of emergency was declared, aimed at preventing a repeat of violence the night before on the anniversary of the police shooting of unarmed black man Michael Brown. Ferguson Anniversary Protests Ferguson Anniversary Protests St Louis County police officers arrest an anti-police demonstrator in Ferguson, Missouri August 11, 2015 Ferguson Anniversary Protests Ferguson Anniversary Protests Protesters march in the rain, Sunday, Aug. 9, 2015, in Ferguson, Mo. Sunday marks one year since Michael Brown was shot and killed by Ferguson Police Officer Darren Wilson. Ferguson Anniversary Protests Ferguson Anniversary Protests Demonstrators, marking the one-year anniversary of the shooting of Michael Brown, march along West Florrisant Street in a driving rain on August 9, 2015 in Ferguson, Missouri. There are reports that two people were shot when gun fire broke out during protests later in the evening. Brown was shot and killed by a Ferguson police officer on August 9, 2014. His death sparked months of sometimes violent protests in Ferguson and drew nationwide focus on police treatment of black offenders. Ferguson Anniversary Protests Ferguson Anniversary Protests A St. Louis County police officers respond in an MRAD vehicle after shots were fired during a protest march on August 9, 2015 on West Florissant Avenue in Ferguson, Missouri. Over 50 shots were reportedly exchanged on the day marking the one year anniversary of the death of an unarmed black teen, Michael Brown, who was shot and killed by a white police officer, throwing America's troubled race relations into harsh relief. Ferguson Anniversary Protests Ferguson Anniversary Protests Protesters yell as police form a line across West Florissant Ave., Sunday, Aug. 9, 2015, in Ferguson, Mo., before shots were fired near the protest. The one-year anniversary of Michael Brown's death in Ferguson began with a march in his honor and ended with a protest that was interrupted by gunfire. Ferguson Anniversary Protests Ferguson Anniversary Protests Protesters fall to the ground to take cover after shots were fired in a police-officer involved shooting in Ferguson, Missouri August 9, 2015. Two people were shot in the midst of a late-night confrontation between riot police and protesters, after a day of peaceful events commemorating the fatal shooting of Michael Brown by a white officer one year ago. Ferguson Anniversary Protests Ferguson Anniversary Protests A white woman holds a black woman as they pray during a rain storm at the site of last year's riots on the one year anniversary of the killing of Michael Brown in Ferguson, Missouri August 9, 2015. Hundreds of people marched, prayed and observed a moment of silence in Ferguson, Missouri, on Sunday, a year to the day after a white police officer shot the unarmed black teenager to death, igniting months of protests and a national debate on race and justice. Ferguson Anniversary Protests Ferguson Anniversary Protests A woman reacts after shots were fired in a police-officer involved shooting in Ferguson, Missouri August 9, 2015. Two people were shot in the midst of a late-night confrontation between riot police and protesters, after a day of peaceful events commemorating the fatal shooting of Michael Brown by a white officer one year ago. Ferguson Anniversary Protests Ferguson Anniversary Protests Police take cover as a barrage of gunfire erupts along West Florrisant Street during a demonstration to mark the 1-year anniversary of the shooting of Michael Brown on August 9, 2015 in Ferguson, Missouri. Brown was shot and killed by a Ferguson police officer on August 9, 2014. His death sparked months of sometimes violent protests in Ferguson and drew nationwide focus on police treatment of black offenders. Ferguson Anniversary Protests Ferguson Anniversary Protests Amarion Allen, 11-years-old stands in front of a police line shortly before shots were fired in a police-officer involved shooting in Ferguson, Missouri August 9, 2015. Two people were shot in the midst of a late-night confrontation between riot police and protesters, after a day of peaceful events commemorating the fatal shooting of Michael Brown by a white officer one year ago.

Protests broke out in St Louis on Friday, when a circuit court judge acquitted former St Louis Metropolitan Police officer Jason Stockley on murder charges in the death of Anthony Lamar Smith.

Mr Stockley shot and killed Mr Smith following a police car chase in 2011. Mr Stockley's defence team told the court he shot in self defence, after seeing Mr Smith reach for a gun. State prosecutors disputed this, alleging that the gun was a plant.

St Louis – the site of massive protests following the police shooting of another young black man, Michael Brown, in 2014 – once again descended into protests after the verdict was handed down.

Protesters marched to the home of St Louis Mayor Lyda Krewson on Friday. Most of the protestors were peaceful, but several broke windows at the residence. Protesters have also damaged the public library, thrown bricks at officers, and attempted to block a freeway ramp, police and witnesses say.

Police have used tear gas and pepper spray to disperse protesters. More than 80 people were arrested in connection with the protests on Sunday; at least 32 were arrested earlier in the weekend. Police say nine officers were injured during protests on Friday.

At a press briefing on Monday, Interim Police Chief Lawrence O’Toole promised to prosecute those who caused damage “to the fullest extent of the law”.

“We're in control. This is our city and we're going to protect it,” he said.