Protesters march in the rain. Associated Press Associated Press

US POLICE HAVE declared a state of emergency after a night of unrest in Ferguson, Missouri.

In a statement, St Louis County executive Steve Stenger said the decision was taken ”in light of last night’s violence and unrest in the city of Ferguson, and the potential for harm to persons and property”.

The move comes after an 18-year-old was charged in connection with a shootout in Ferguson after a day of peaceful protests marking one year since the police shooting of unarmed black teenager Michael Brown.

Tyrone Harris – who is accused of first-degree assault on a police officer, armed criminal action and shooting at or from a motor vehicle – is currently in hospital with wounds sustained during the incident.

St Louis County police saying an officer had opened fire after coming under “heavy gunfire” during the shootout.

Pictures on Twitter showed at least two cars with bullet holes.

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Protest groups were quick to criticise the police response to protesters who gathered along West Florissant Avenue last night.

St. Louis County Chief Jon Belmar said at a news conference that officers had been tracking the suspect, who they believed was armed, during a protest marking the death of Brown.

Brown was the black, unarmed 18-year-old whose killing by a white Feguson police officer touched off a national “Black Lives Matter” movement.

Demonstrators had taken to the streets to mark the anniversary of Brown’s death in a fateful encounter on August 9, 2014 with officer Darren Wilson.

The shooting, and a subsequent decision not to indict Wilson, led to violent unrest and set off nationwide protests.

Sunday’s day of remembrance had been peaceful until a handful of protesters grew rowdy later in the evening.

At the height of the rowdy protest in which rocks and bottles were thrown at officers, gunshots rang out from the area near a strip of stores, including some that had been looted.

Belmar believes the shots came from about six different shooters. What prompted the shooting wasn’t clear, but Belmar said the groups had been feuding.

At one point, the suspect crossed the street and apparently spotted the plainclothes officers arriving in an unmarked van with distinctive red and blue police lights, Belmar said. He said the suspect shot into the hood and windshield.

The officers fired back at him from inside the vehicle then pursued him on foot when he ran.

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The suspect again fired on the officers when he became trapped in a fenced-in area, the chief said, and all four officers fired back. He was struck and fell.

The suspect was taken to a hospital, where Belmar said he was in “critical, unstable” condition. Authorities didn’t immediately release the identities of anyone involved, but Tyrone Harris told the St. Louis Post-Dispatch that the injured suspect was his son, 18-year-old Tyrone Harris Jr.

The elder Harris told the newspaper shortly after 3am that his son had just gotten out of surgery.

None of the officers was seriously injured. All four have been put on standard administrative leave. They were not wearing body cameras, Belmar said.

A crowd of about 300 people had gathered earlier to mark the anniversary, during which they observed four and a half minutes of silence and released two white doves.

The time represented the four and a half hours that Brown’s body lay face down in the street before being taken away.

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Many in the crowd wore T-shirts emblazoned with Brown’s portrait and the words “Choose Change”. Others carried signs, including one that read: “STOP killing black children.”

Brown’s father, also called Michael, said he was grateful so many people had turned out for the march:

If it wasn’t for y’all this would be swept under the carpet. So I just want to give my love out to y’all.

In New York, dozens of people gathered at Union Square to hold a vigil for Brown in solidarity with Ferguson and to call for ongoing demonstrations against police killings of minorities.

Members of the St. Louis County Police Department take cover. Associated Press Associated Press

About 100 people gathered in Brooklyn earlier, staging a symbolic “die-in” to protest Brown’s shooting. Police arrested several people.

One year on, black leaders say they have witnessed a dramatic change in American attitudes toward race, but see little action by lawmakers to enact policing reforms.

Yet another high-profile shooting occurred Friday, when a Texas police officer fatally shot 19-year-old unarmed college football player Christian Taylor after he drove his vehicle through the front of a car dealership.

- © AFP 2015 with reporting by Associated Press

Read: Video emerges of Christian Taylor shortly before he was shot dead >

Originally published: 21.40