Donald Trump's ex-chief of staff quits diplomatic post after US Capitol attack

"I can't stay here, not after yesterday. You can't look at that yesterday and think I want to be a part of that in any way, shape or form," Mulvaney told CNBC television.

Mulvaney, who had been moved from chief of staff to special envoy for Northern Ireland, said he told the US Secretary of State Mike Pompeo that he was resigning.

"I can't do it. I can't stay," he told CNBC, which has given a signal that other White House staff were also eying the exits.

"Those who choose to stay, and I have talked with some of them, are choosing to stay because they're worried the president might put someone worse in," he said.

At least four people died on Wednesday as supporters of outgoing President Donald Trump stormed into the iconic Capitol building and created chaos over his defeat in the polls.

More than 50 people have been detained in the course of violent protests at the US Capitol on Wednesday, claimed police.

Shortly after 1 p.m. ET Wednesday hundreds of pro-Trump protesters pushed through barriers set up along the perimeter of the Capitol, where they tussled with officers in full riot gear, some calling the officers "traitors" for doing their jobs, CNN reported.

Vice President Mike Pence was evacuated from his chamber.