More than 300 US news organisations will launch a free press campaign on Thursday to counter President Donald Trump's attacks.

The Boston Globe made the call last week for a nationwide denouncement of the president's "dirty war" against the media, using the hashtag #EnemyOfNone.

Mr Trump has derided media reports as "fake news" and attacked journalists as "enemies of the people".

UN experts have said this raises the risk of violence against journalists.

The Boston Globe pledged to write an editorial "on the dangers of the administration's assault on the press" on 16 August, and asked others to do the same.

Major US national newspapers and smaller local outlets have vowed to answer the call, as have international publications like the UK newspaper The Guardian.

Mr Trump is the first president "who appears to have a calculated and consistent policy of undermining, delegitimising and even endangering the press's work," the London-based newspaper wrote in its editorial.

Under the headline A Free Press Needs You, the New York Times called Mr Trump's attacks "dangerous to the lifeblood of democracy", and published excerpts from dozens more publications beneath.

In its own editorial, under the headline Journalists Are Not The Enemy, the Boston Globe said a free press had been a core American principle for more than 200 years.

"Today it is under serious threat," it reads, arguing that such treatment of the press by the US president "sends an alarming signal to despots" worldwide.

Thursday's campaign comes after a series of incidents and Trump remarks ramping up pressure on the media.

While Mr Trump's daughter Ivanka distanced herself from her father's media attacks, White House press secretary Sarah Saunders refused to say the media were not an enemy of the people.

And at a presidential rally in Florida in July, CNN filmed Mr Trump's supporters yelling insults and swearing at reporters covering the event. CNN presenter Jim Acosta tweeted a clip, which contained strong language.