Irish journalist Declan Walsh has said US President Donald Trump's criticism of the media is threatening journalism around the world.

Speaking to RTÉ News, he said there is an "unwritten assumption" that the US government will step-in in extreme "moments of peril for reporters who work for American papers".

The New York Times reporter said he believes that under the Trump administration, that assumption has been challenged.

Mr Walsh said with President Trump regularly describing reporters as "enemies of the people", it has given countries like Egypt the permission to do what they want to the media without being reprimanded.

Two years ago Mr Walsh reported on a story about an Italian student who was killed in Cairo as the Italian government said the responsibility lay with the Egyptian government for his death.

After Mr Walsh reported the story, he said he knew it was going to be sensitive but he did not expect the Egyptians to take such drastic action so quickly.

Once the paper got a tip off from an American official that he could be arrested, Mr Walsh said the only option "was to get out quickly" as he knew Egypt did not have a good track record detaining journalists.

He pointed to the case of Peter Greste - an Australian journalist who was detained in the country for over a year.

"I am hugely grateful ... to the Irish government and to our own diplomats who reacted very quicky. [They] were very cool, calm and drove me straight to the airport and provided me all the protections that they could afford" he said.

As the Department of Foreign Affairs in Dublin said it is not commenting on the report, Declan Walsh said it is fortunate he is an Irish citizen because his US colleagues may not have the same protections.

An organisation which helps human rights defenders and journalists has said that these professions are being targeted around the world.

Frontline Defenders Executive Director Andrew Anderson told RTÉ News that there are around 226 journalists in jail around the world.

Mr Walsh said the whole incident raises larger questions though, particularly for American media, about whether the Trump administration is willing, or not, to step in and help them.