Washington, Jan 8 (IANS): US Transportation Secretary Elaine Chao has announced her resignation in protest over the chaos and violence that rocked Capitol Hill.

With her resignation announced on Thursday, Chao, who is the wife of Senate Majority Leader Mitch McConnell, became the first member of outgoing President Donald Trump's cabinet to step down in the wake of Wednesday's protests, Xinhua news agency reported.

In a letter to her colleagues at the Department of Transportation, Chao said her resignation will take effect on January 11.

"Yesterday, our country experienced a traumatic and entirely avoidable event as supporters of the President stormed the Capitol building following a rally he addressed.

"As I'm sure is the case with many of you, it has deeply troubled me in a way that I simply cannot set aside.

"It has been the honour of a lifetime to serve the US Department of Transportation," she added in the letter.

Chao also mentioned that "we will help my announced successor (South Bend) Mayor Pete Buttigieg with taking on the responsibility of running this wonderful department".

The 67-year-old has served as Transportation Secretary since 2017.

She was previously the Labour Secretary under former President George W. Bush from 2001 to 2009.

Protesters in support of Trump's futile efforts to reject the 2020 presidential election results breached the Capitol on Wednesday afternoon, when Congress met to affirm President-elect Joe Biden's Electoral College victory.

Chaos and violence forced an hours-long lockdown on the Capitol grounds, which also left four people dead, with multiple injuries and dozens of arrests.

Trump has been roundly criticised for inciting the unrest with unproven claims that the election was fraudulent.