The white officer who shot dead unarmed black teenager Michael Brown in Ferguson, Missouri, has resigned from the police force.

Four months after the confrontation that fuelled violent protests in the St Louis suburb and across the US, Darren Wilson quit the Ferguson Police Department.

Mr Wilson has been on administrative leave since the shooting on August 9th.

His resignation was announced on Saturday by one of his attorneys, Neil Bruntrager, who said it takes effect immediately.

According to the St Louis Post-Dispatch newspaper, Mr Wilson (28) sent a resignation letter to the Ferguson force which read: "It was my hope to continue in police work, but the safety of other police officers and the community are of paramount importance to me."

"I have been told that my continued employment may put the residents and police officers of the City of Ferguson at risk, which is a circumstance that I cannot allow."

"It is my hope that my resignation will allow the community to heal."

A grand jury spent more than three months reviewing evidence in the case before deciding not to issue any charges against him last week.

He had told jurors that he feared for his life when Mr Brown (18) hit him and grabbed for his gun.

The US Justice Department is still conducting a civil rights investigation into the shooting and a separate probe of police department practices.

The shooting ignited a national debate about race and police power.

Mr Wilson spent months in hiding after the shooting, which he claimed was in self-defence.

He broke his silence after the grand jury decision, saying he could not have done anything differently in the encounter with Mr Brown.

Mr Wilson told ABC News he has a clean conscience because "I know I did my job right".

Mr Brown's shooting was the first time he fired his gun on the job, he said.

Asked whether the encounter would have unfolded the same way if Mr Brown had been white, Mr Wilson said "yes".

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Mr Wilson began his career in nearby Jennings before moving to the Ferguson job a few years ago.

He had no previous complaints against him and a good career record, according to Police Chief Thomas Jackson, who described Mr Wilson as "an excellent police officer".

A few months before the shooting, Mr Wilson had received a commendation for detaining a suspect in a drugs case.

Meanwhile, police detained 16 people after fresh protests hit Ferguson on Black Friday, one of the busiest shopping days of the year, and arrests were made across the country during similar rallies.

Police said only one of those arrested was from the St Louis area. Nine were from New York, three from Chicago, two from California and one from Iowa.

All were held on misdemeanour peace disturbance charges, except for one who was detained on suspicion of assaulting a police officer and resisting arrest.