More than 20 people have been arrested in Ferguson, Missouri, amid protests marking the anniversary of the death of unarmed black teenager Michael Brown.
A state of emergency was declared, as officers in riot gear forced people off the streets on Monday night.
A police spokesman said 23 people were detained, but “there were no shots fired, no smoke or tear gas used”.
On Sunday, Tyrone Harris, 18, was critically wounded after being fired on by police in Ferguson.
The authorities say Mr Harris was armed and opened fire, but his father has described their account of events as “a bunch of lies”.
Prosecutors have filed 10 charges against him, including assaulting an officer.
The shooting followed a day of peaceful and sombre commemorations in memory of Michael Brown.
The 18-year-old was shot in August 2014 by a white police officer who was later cleared of any wrongdoing by a grand jury and the US Department of Justice.
The death triggered a wave of protests over alleged racism and the use of excessive force by US police officers.
On Monday night marchers chanted, beat drums and carried signs in memory of Brown – but some demonstrators also attacked officers, according to the St Louis police department.
It tweeted: “Officers are being hit with rocks and bottles. We continue to support free speech, but agitators who ignore orders to disperse risk arrest.”
By early morning on Tuesday, most people had left the areas where confrontations had occurred.
‘Give us space’
Ferguson resident Roberta Lynch, 51, said relations with police had not improved in the year since Michael Brown’s death.
“They are doing the same old stuff, taking our rights,” she said. “They need to give us our space.”
Earlier on Monday, police arrested about 50 protesters – including civil rights activist Cornel West – who staged a sit-in outside the main courthouse in St Louis.
Other protesters also 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.
What happened in Ferguson in 2014?
The state of emergency – designed to allow to take control in and around Ferguson – was issued on Monday afternoon by St Louis County Executive Steve Stenger and authorised by county Police Chief Jon Belmar.
According to police, a gunfight erupted between two rival groups in West Florissant Avenue and a suspect, whom they identified as Tyrone Harris, then shot at plain-clothes police officers, who returned fire.
Police Chief Belmar said those who had opened fire on the officers “were criminals, they weren’t protesters”.
But Mr Harris’s father said his son had been unarmed and was “running for his life”.
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.
Campaigners were further incensed when a justice department investigation found widespread racial bias in the Ferguson police force.
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