President Donald Trump has lashed out at the press as newspapers across the US launched a co-ordinated rebuttal to his attacks against what he calls "fake news".

In a series of morning Twitter posts, Trump said The Boston Globe was "in collusion" with other newspapers for leading the editorial effort. Trump added in a tweet, "PROVE IT!" though it was unclear what he meant.

Trump tweeted that he supported a free press, but much of what the US press printed was "fake news".