Trump's charge of media "collusion" highlights his acrimonious relationship with the press, which he often accuses of bias against him. He's particularly enraged by coverage of special counsel Robert Mueller 's investigation of potential collusion between the Trump campaign and Russia.

Trump also claimed in that tweet that The New York Times had purchased the Globe for $2.1 billion, and had sold it two decades later for just $1. A Times report announcing that 2013 sale , however, shows that the paper was bought in 1993 for $1.1 billion and sold for $70 million.

"The Globe is in COLLUSION with other papers on free press," Trump said in a tweet. "PROVE IT!" he added, without elaborating.

President Donald Trump attacked The Boston Globe in a tweet on Thursday after it coordinated efforts with hundreds of newspapers across the country to publish editorials defending a free press.

At campaign-style rallies and on social media Trump regularly calls the mainstream media "fake news" and "the enemy of the people." He has increasingly taken to Twitter to rail against the Mueller probe, calling the investigation a "rigged witch hunt" and saying there was "no collusion" between his campaign and Russia.

The Globe's coordinated efforts resulted in editorials in more than 350 outlets pushing back against Trump's attacks.

"For more than two centuries, this foundational American principle has protected journalists at home and served as a model for free nations abroad. Today it is under serious threat," the Globe's editorial board wrote. "And it sends an alarming signal to despots from Ankara to Moscow, Beijing to Baghdad, that journalists can be treated as a domestic enemy."

In a follow-up tweet Thursday, Trump asserted that "there is nothing that I would want more for our Country than true FREEDOM OF THE PRESS." He then repeated his "FAKE NEWS" taunt.

Trump tweet Globe 2

The First Amendment to the U.S. Constitution states that Congress cannot enact laws prohibiting the freedom of the press. Trump's critics have argued that the president's continued attacks on the media create a chilling effect that hinders press freedom.

Later on Thursday, the Senate unanimously passed a resolution condemning "attacks on the institution of the free press." It was pushed by Senate Minority Leader Sen. Chuck Schumer, D-N.Y., as well as Democratic Sens. Brian Schatz of Hawaii and Connecticut's Richard Blumenthal.

The document affirmed that the Senate "views efforts to systematically undermine the credibility of the press as an attack on the democratic institutions of the United States." A source familiar with the resolution said it was introduced today in order to line up with the spree of free-press editorials.