NEW YORK -Hillary Clinton has excoriated Donald Trump, telling an audience in New York press rights and free speech are "under open assault" under an administration she compared to an authoritarian regime, the Associated Press reported.

"We are living through an all-out war on truth, facts and reason," Clinton said at the PEN America World Voices Festival in Manhattan on Sunday (April 22), according to US media.

"When leaders deny things we can see with our own eyes, like the size of a crowd at the inauguration, when they refuse to accept settled science when it comes to urgent challenges like climate change … it is the beginning of the end of freedom, and that is not hyperbole. It's what authoritarian regimes through history have done."

The former presidential candidate, secretary of state, senator and first lady was delivering the Arthur Miller Freedom to Write lecture. She began by discussing threats to press freedom and free speech including in Vladimir Putin's Russia, the Associated Press said. But she soon turned her remarks to the US under Trump, saying such freedoms were "in the most perilous position I've seen in my lifetime".

"Today we have a president who seems to reject the role of a free press in our democracy," she said according to US media.

"Although obsessed with his own press coverage, he evaluates it based not on whether it provides knowledge or understanding, but solely on whether the daily coverage helps him and hurts his opponents.

"Now, given his track record, is it any surprise that according to the latest round of revelations, he joked about throwing reporters in jail to make them talk?"

She was referring to the newly declassified memos that former FBI director James Comey kept, recounting his private conversations with Trump, who fired him last year.

It was Clinton's only reference to Comey.

According to those notes, Comey and Trump agreed that those who leaked classified information should be aggressively prosecuted. Comey said he was in favor of "putting a head on a pike as a message."

Trump, according to Comey's telling, suggested that reporters who publish the leaks should be jailed, adding: "They spend a couple days in jail, make a new friend, and they are ready to talk."

Clinton and Trump have exchanged barbs since he entered the White House. She has repeatedly questioned his fitness for office, and Trump has frequently called her "Crooked Hillary" in posts on Twitter.

The White House did not immediately respond to a request for comment.

Clinton's remarks were followed by a conversation with novelist Chimamanda Ngozi Adichie. Under friendly questioning, Clinton was asked if she had "hit back" enough during the campaign - a reference to a childhood episode in which, Clinton has written, her mother gave her permission to hit back at a bully.

"I now think that I didn't," Clinton said. She described the much-discussed moment when Trump was "stalking me on that debate stage". She recalled thinking: "What do I do? Do I turn around and say: 'Back up, you creep?"' But then, she said, "the coverage would have been, 'She can't take the pressure, she got angry."'

And so, she said she told herself: "You just have to be calm and in control. Because ultimately what the country wants is someone who is not blowing up in the Oval Office."

"Well, you know that did not work out so well," she said, to laughter.