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President Donald Trump says federal law enforcement will be sent to Kenosha, Wisconsin, following unrest sparked by the police shooting of a black man.
Jacob Blake, 29, was shot and injured by police on Sunday as he leaned into his car as his children watched.
Protests have been ongoing for several nights, and on Tuesday, two people were shot dead and another was injured. A teenager has been charged with murder.
Mr Blake is recovering in hospital and is conscious, his family say.
But his lawyers say it will take “a miracle” for him to walk again.
Announcing his move in a tweet on Wednesday, Mr Trump said: “We will NOT stand for looting, arson, violence, and lawlessness on American streets. My team just got off the phone with Governor Evers who agreed to accept federal assistance (Portland should do the same!).”
Shortly following Mr Trump’s tweet, Wisconsin Governor Tony Evers said he had authorised 500 National Guard troops to support law enforcement efforts.
Earlier, police in neighbouring Illinois said they arrested a 17-year-old on suspicion of first-degree murder.
