WASHINGTON (AP) -- President Donald Trump is unleashing new criticism of the investigations into possible ties between his campaign associates and Russia.

Trump -- in a series of tweets -- is making reference to what he calls "phony Trump/Russia `collusion,' which doesn't exist." He says Democrats are using -- in his words -- a "witch hunt" for "evil politics" and adds that Republicans are "fighting back like never before."

Trump's tweets follow a CNN report that a federal grand jury in Washington has approved the first charges in the criminal investigation led by special counsel Robert Mueller.

The Associated Press hasn't confirmed the CNN report.

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