Image copyright Getty Images Image caption Police were seen collecting evidence on Monday a day after the incident

Prosecutors in Ferguson, Missouri, have charged a man with assaulting officers during events marking the first anniversary of the killing of unarmed black teenager Michael Brown.

They named the suspect as Tyrone Harris, 18, who was critically wounded in a gun battle with police on Sunday.

The authorities have declared a state of emergency in the city.

Michael Brown's death triggered a wave of demonstrations over the use of excessive force by police officers.

Brown, 18, was shot in August 2014 by white police officer Darren Wilson, who was later cleared of any wrongdoing by a grand jury and the US Department of Justice.

What happened in Ferguson in 2014?

Image copyright AP Image caption Prominent activist Cornel West was among those arrested in St Louis on Monday

Separately on Monday, about 50 people were arrested - including civil rights activist Cornel West - after blocking the main courthouse in St Louis.

The protesters were calling for the US government to disband the Ferguson Police Department, the St Louis Post-Dispatch reported.

Other protesters later briefly blocked a major highway - Interstate 70 - during the afternoon rush hour and a number of arrests were made.

The demonstrations were part of a day of civil disobedience called by activists in St Louis and other major US cities.

At the scene: Aleem Maqbool, BBC News, Ferguson

Once again in Ferguson there is discussion about whether a violent incident has detracted from the message of the hundreds who took to the streets peacefully; a message that they still feel policing here and across America is racist.

Many in Ferguson have said that they feel there is a better way than confrontation to convey the hurt and frustration felt by the community.

But even in speeches during the day, others expressed frustration that protesters were being told to be peaceful, when so many young black men had faced violent deaths in encounters with the police.

We are often reminded here that it is the confrontation and images of violence a year ago that made the country sit up and take notice, and it is what brought the subsequent media attention to the issue that persisted throughout the months. But to what end?

On Sunday, hundreds of people stood silent for four-and-a-half minutes at the spot where Michael Brown was killed in Ferguson, representing the number of hours that his body lay in the street unattended.

But the day of peaceful and sombre commemorations turned violent late at night when, according to police, a gunfight erupted between two rival groups on West Florissant Avenue.

Police say Mr Harris was armed and opened fired, but his father has described their account of events as "a bunch of lies".

Prosecutors filed 10 charges against him, including assaulting an officer.

Police said he was among six people who fired at an unmarked SUV with plainclothes detectives inside, who then fired back.

Image copyright Getty Images Image caption Prosecutors filed 10 counts against Tyrone Harris (pictured lying injured on the ground)

The man's father told the AP news agency that his son, a close friend of Brown, was shot between eight and 12 times as he was running away.

In a statement on Monday, Ferguson Mayor James Knowles III said the city was "deeply disappointed" by Sunday's violence and urged local people to be "watchful for those who want to cause harm to our community".

"This kind of behaviour is counterproductive, and cannot be tolerated if we want to continue bettering the community for all our residents," he said.

Announcing a state of emergency on Monday, authorities in St Louis county placed police chief Jon Belmar in charge of Ferguson and the surrounding areas.

US attorney Loretta Lynch denounced Sunday's violence.

"As we have seen over the recent months and years, not only does violence obscure any message of peaceful protest, it places the community, as well as the officers who seek to protect it, in harm's way," she said.

Protest groups, including the Ferguson Action Council and Organization for Black Struggle, described Sunday's police response as "excessive".

Media playback is unsupported on your device Media caption Demonstrators confronted police on the streets of Ferguson exactly a year after Michael Brown's death, as Aleem Maqbool reports

John Gaskin III, a member of US rights group NAACP, told AP he did not expect unrest to escalate in Ferguson in the same way it has over the past year.

However, he warned that not many people would believe the police account of Sunday night's events as "there's still a tremendous level of distrust between law enforcement and the community".

There have been a number of high-profile shootings of unarmed black men in US cities in recent months.

The most recent case involved 19-year-old Christian Taylor who was shot dead by a white police officer after he was spotted on surveillance footage vandalising cars in Arlington, Texas, on Friday.

The nationwide protest movement was further incensed when a justice department investigation found widespread racial bias in the Ferguson police force.

US Dept of Justice report on Ferguson racism