Image copyright Reuters Image caption The protests began on Friday over the acquittal of former police officer Jason Stockley

Police in St Louis, Missouri, have come under fire for chanting after clearing protests over the acquittal of an officer who shot dead a black man.

The chant, "whose street, our street", is a phrase often repeated by those demonstrating against the verdict.

Jason Stockley, 36, was cleared on Friday of murdering Anthony Lamar Smith, 24, who was fatally shot after a police pursuit in 2011.

More than 120 people were arrested after a third night of raucous protests.

Hundreds of police dressed in riot gear patrolled downtown St Louis on Sunday night, making arrests and seizing at least five weapons, Police Chief Lawrence O'Toole said early on Monday.

"I'm proud to tell you the city of St Louis is safe and the police owned tonight," he said at a news conference. "We're in control. This is our city and we're going to protect it."

Hours earlier, some members of the police department sparked outrage when they were heard chanting, "whose street, our street," after breaking up demonstrations, according to US media reports.

St Louis Post-Dispatch photographer David Carson, who first reported the chant, tweeted the commander at the scene did not hear the chant, but said it was not acceptable and he would address it.

Mr Carson also tweeted footage purporting to show police officers chanting the phrase.

Skip Twitter post by @PDPJ I spoke with the commander at the scene, he said he did not hear the chant, but said chant was not acceptable, said he would deal with it. — David Carson (@PDPJ) September 18, 2017 Report

Some officers had chemicals and rocks thrown at them, police said.

Their injuries were described as "minor or moderate" and the perpetrators as a "group of criminals".

"Today we saw again the vast majority of protesters are non-violent," St Louis Mayor Lyda Krewson said.

"But for the third day in a row the days have been calm but the nights have been destructive."

Police posted images to Twitter of weapons reportedly confiscated in the city.

The protests began on Friday immediately after the court verdict. Weekend concerts by the Irish rock band U2 and British artist Ed Sheeran were cancelled due to security concerns.

Mr Smith was a new father and engaged to be married when he was killed on 20 December 2011.

Image copyright CBS Image caption Anthony Lamar Smith failed to follow police commands, defence lawyers argued in court

The St Louis Metropolitan Police Department initially deemed the killing justifiable.

Mr Stockley left the police department and moved to Texas in August 2013.

But the investigation continued and he was charged last year after prosecutors cited unspecified new evidence.

Image copyright Reuters Image caption The city's mayor said the "vast majority of protestors are non-violent"

Mr Stockley and his partner said they believed they had seen Mr Smith engaging in a drug deal outside a restaurant.

Police dashcam video and surveillance footage showed Mr Smith reversing his car into the police vehicle twice during his attempt to drive off.

After a three-minute high-speed chase, Mr Stockley told his partner, who was in the driver's seat, to ram Mr Smith's car.

Dashcam video from the police cruiser recorded him saying he was "going to kill this [expletive]".

Mr Stockley then ran to Mr Smith's window and fired five shots, hitting him each time.

His defence team argued the recording could not prove intent and Mr Stockley testified in court that he could not remember making such a statement.

The cases where US police have faced killing charges

The case has inflamed racial tensions in St Louis, which has one of the highest murder rates in the US.

Rioting erupted in 2014 in nearby Ferguson, Missouri, after the fatal police shooting of an unarmed black teenager, Michael Brown.