In a broad condemnation of Trump's conduct in office, Zeid Ra'ad Al Hussein said he viewed the US presidency as the driver of "the bus of humanity", accusing Trump of "reckless driving".
Zeid, the United Nations High Commissioner for Human Rights, also blasted Trump's decision to pardon former Arizona sheriff Joe Arpaio, who was convicted of criminal contempt last month for illegally profiling Hispanic immigrants.
On the media, Zeid voiced particular alarm over Trump's verbal assaults on CNN, the New York Times and Washington Post.
"To call these news organisations 'fake' does tremendous damage and to refer to individual journalists in this way, I have to ask the question, is this not an incitement for others to attack journalists?
"And let's assume a journalist is harmed from one of these organisations, does the president not bear responsibility for this, for having fanned this?" Zeid told reporters in Geneva.
"I believe it could amount to incitement," he added, saying Trump had set in motion a cycle that includes "incitement, fear, self-censorship and violence."
According to the rights chief, Trump's assault on the media has emboldened other countries to crack down on press freedoms.
"The demonisation of the press is poisonous because it has consequences elsewhere," Zeid said.
He expressed specific concern over Trump's speech in Arizona earlier this month in which journalists were condemned by the US leader as "dishonest people" who "don't like our country".
Supports 'racial profiling'?
Turning to the pardon for Arpaio, a hugely controversial figure intially targeted for prosecution by former president Barack Obama's justice department, Zeid said he was deeply disturbed by Trump's decision.
"I had to ask myself the question what does this mean? Does the president support racial profiling of Latinos in particular? Does he support abuse of prisoners?
"Arpaio at one stage referred to the open air prison that he set up as a 'concentration camp'", Zeid said, asking "does the president support this?"
Arpaio, who was known to make detainees wear pink underwear to humiliate them, housed prisoners in tent camps surrounded by barbed wire, in the scorching Arizona desert.
The former sheriff once likened the encampment to a concentration camp, although he later backed away from that remark.
Reacting publicly for the first time to the recent unrest in Charlottesville, Virginia, Zeid denounced the racist and anti-semitic actions of neo-Nazi and white supremacists demonstrators as "an abomination" and "a nightmare."
Zeid, who has not minced his words in previous criticism of Trump, indicated that the world was is in a perilous state with the New York billionaire in a position of global leadership.
"I almost feel that the president is driving the bus of humanity and we are careening down a mountain pass and, in taking these measures, at least from a human rights perspective it seems to be reckless driving," he told reporters.
"You asked me in November if I thought he was dangerous," Zeid continued. "Today the only person who can confirm that is the president himself by dint of his own actions."
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