FERGUSON (Reuters/AFP) - St. Louis County on Friday ended the state of emergency it had put in effect earlier this week for Ferguson, Missouri, and surrounding areas due to violent street protests.

"After reviewing the events of the past four evenings, under the state of emergency, I am pleased to report our law enforcement officers have established order while preventing further acts of violence in Ferguson," St Louis County Executive Steve Stenger said in a statement.

"I want to emphasise local law enforcement will remain vigilant, and officers are prepared to respond swiftly if necessary."

The county had declared the state of emergency after peaceful protests marking the first anniversary of the police shooting of black teen Michael Brown devolved into violence and looting on Sunday night.

Tyrone Harris, 18, was shot by police after allegedly opening fire during the chaos.

Unrest broke out again on Monday night as angry demonstrators threw stones and bottles at police.

The following nights were peaceful with no arrests, officials said.

Brown's death on August 9, 2014, led to weeks of sometimes violent unrest in Ferguson last year and sparked nationwide protests.

Outrage at the deaths of Brown and a series of others killed by police in disputed circumstances have fueled the Black Lives Matter movement and a national conversation about racism and police tactics.