The UN human rights chief said Wednesday that President Donald Trump's relentless attacks on the media could trigger violence against journalists, suggesting the US leader would be responsible.

"I believe it could amount to incitement," Zeid Ra'ad Al Hussein said, referring to Trump's verbal attacks on major US news outlets like the New York Times and CNN.

"Let's assume a journalist is harmed from one of these organisations, does the president not bear responsibility for this?" Zeid added, saying Trump had set in motion a cycle that includes "incitement, fear, self-censorship and violence."