US police have made numerous arrests during a tense night-time stand-off in Ferguson, after St Louis County declared a state of emergency and a teenager was charged with shooting at police officers.

Protesters on the streets beat drums and chanted as bottles and rocks were thrown, while police used pepper spray as they detained demonstrators during the stand-off, which continued into the early hours of Tuesday morning.

“Officers are being hit with rocks and bottles. We continue to support free speech, but agitators who ignore orders to disperse risk arrest,” tweeted the St Louis County police department.

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The protests came after unrest and a shootout in Ferguson on Sunday night that led county officials to declare a state of emergency on Monday.

St Louis County executive Steve Stenger said county police would immediately take charge of “police emergency management” in Ferguson and surrounding districts.

“In light of last night’s violence and unrest in the city of Ferguson, and the potential for harm to persons and property, I am exercising my authority as county executive to issue a state of emergency, effective immediately,” he said in a statement.

His statement was issued as an 18-year-old was charged in connection with the shootout in Ferguson on Sunday, following a day of mostly peaceful protests marking the first anniversary of the fatal police shooting of unarmed black teenager Michael Brown.

Tyrone Harris is accused of first-degree assault on police officers, armed criminal action and shooting at a motor vehicle, police said.

Harris, from Northwoods, another section of St Louis County, remained in hospital on Monday with wounds sustained in the shootout.

In St Louis city centre, more than 50 protesters were arrested after climbing the barricade around a federal courthouse during a midday demonstration, local news media reported.

Media reports late on Monday said protesters had blocked a main highway, Interstate 70, just outside Ferguson.

Demonstrators were also arrested elsewhere in town, including scholar and activist Cornel West, Complex magazine reported.
Early on Tuesday morning a crowd of about 100 protesters remained on the streets of Ferguson.

– AAP