This week in Oakland, California, demonstrators have taken to the streets on consecutive nights to protest against two separate US grand jury decisions not to prosecute white police officers who killed unarmed black men.

On Wednesday night around 100 people marched against police violence when, according to reports, two members of the protest began inciting them to, um, be violent.

However, some members of the crowd realised the two men wearing scarves over their faces weren't all they seemed and accused them of being undercover police officers.

At this point the two men did identify themselves as plainclothes members of the California Highway Patrol.

That force's chief, Avery Browne, said that the two detectives - there to gather intelligence and nothing more - were surrounded by up to 50 demonstrators who did not back off even when one of the two took out a police baton, forcing one to draw his gun and point it at the crowd.

The Oakland Police Department said it would look into claims that officers from a separate force were trying to incite demonstrators to violence.

Pictures: Noah Berger/Reuters

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