A state of emergency is in force in the US city of Ferguson amid protests marking the anniversary of the death of black teenager Michael Brown, according to the BBC.

The city is reported to be tense after another black teenager was critically wounded in a gun battle with police on Sunday.

Tyrone Harris, 18, was later charged with assaulting police officers.

Missouri Governor Jay Nixon has appealed for protests to remain peaceful.

Michael Brown, 18, 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 police officers.
Late on Monday, police arrested several protesters who blocked a traffic lane on West Florissant Avenue - the site of previous unrest. Witnesses said some people in the crowd threw water bottles at officers but there were no reports of violence.

Earlier, 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.

The state of emergency was issued on Monday afternoon by St Louis County Executive Steve Stenger and authorized county Police Chief Jon Belmar to take control in and around Ferguson.

Sunday's shooting came after a day of peaceful and somber commemorations in memory of Michael Brown.