Police charged a young African-American man on Sunday in connection with the shooting in Ferguson last week that wounded two police officers and rekindled tension in the racially troubled Missouri city.

Jeffrey Williams, 20, is charged with first-degree assault, armed criminal action and shooting a firearm from a motor vehicle causing injury, St. Louis County prosecutor Robert McCulloch told reporters, after an intense four-day manhunt.

"It's possible at this point that he was firing shots at someone other than the police, but struck the police officers," McCulloch said, adding that Williams had acknowledged firing gunshots and that the investigation was ongoing.

Ferguson has been in the global spotlight since a white policeman fatally shot unarmed black teenager Michael Brown in August, igniting sometimes violent protests in major American cities and prompting an impassioned debate about policing and race relations.

Wednesday night's gunfire erupted just hours after Ferguson's police chief resigned in response to a Justice Department report that alleged systemic racial bias in the city's overwhelmingly white police force, in a suburb of 21,000 that is two-thirds black.

McCulloch said Williams had participated in some of the demonstrations demanding justice that have roiled Ferguson almost nightly since Brown's killing -- a claim disputed by protest organizers.

After news filtered through of Williams' arrest, about 100 people gathered outside the police station in support of police and Mayor James Knowles, who is under growing pressure to resign.

Facing them were a handful of African-American protesters, some of whom shouted abuse in the faces of the predominantly white and middle-aged pro-police group.

"Police officers are human beings and most police officers are doing a very good job," said white Ferguson resident Blake Ashby, who sported a yellow "Ferguson Proud" T-shirt but acknowledged a need for institutional reforms.

In Washington, Attorney General Eric Holder welcomed news of Williams' arrest, saying it sent "a clear message that acts of violence against our law enforcement personnel will never be tolerated."

'Never seen his face'

Protest organizers -- including a pastor who knows the Williams family -- strongly disputed the assertion that the suspect had taken part in anti-police demonstrations, saying they did not recognize him.

"I've never seen his face (at the protests)," said Bishop Derrick Robinson, who visited Williams in his cell in the St. Louis County jail on Sunday.

Robinson told AFP that Williams told him he had shot at a demonstrator who had attempted to rob him, but that he could not identify who that perpetrator was.

The pastor added that Williams showed him bruises on his body, which the detainee claimed had been the result of police beating him when he was taken into custody Saturday.

The two officers shot Wednesday were among a detail of several dozen police from around St. Louis County who had been sent to Ferguson as reinforcements.

One, from the affluent white suburb of Webster Groves, was hit in the face, the other, a member of the St. Louis County force, in the shoulder. Both were treated in the hospital then released.

According to McCulloch, Williams -- being held on $300,000 cash bail -- "has acknowledged his participation in firing the shots," adding however that "he is innocent until proven guilty."

He also said a .40 caliber handgun that matched the shells found at the scene of the shooting had been found during a raid of Williams' residence in the Ferguson area.

Next to quit?

Missouri has some of the most relaxed gun laws in the United States. No permit is needed to buy or own a handgun in the Midwestern state and open-carry is permitted.

It was unclear how the arrest would impact Ferguson, where McCulloch has been criticized after a St. Louis County grand jury for which he was responsible did not indict Darren Wilson, the officer who killed Brown.

In the damning report earlier this month, the Justice Department said Ferguson's police department and municipal court targeted African Americans in an attempt to collect fines and court fees to fill up city coffers.

Besides police chief Thomas Jackson, the city's manager, municipal judge and two police officers have resigned, and a clerk was fired for writing racist emails.

Mayor Knowles is under growing pressure to resign as well, but in interviews with US news media he has said he intends to stay in office to implement reforms and restore community harmony.