The head of the US Secret Service, tasked with guarding US President Barack Obama, has resigned following several high-profile security lapses.

Julia Pierson offered her resignation to the Secretary of the Department of Homeland Security on Wednesday.

A day earlier, she faced angry questions in Congress about a major breach of White House security.

News of another incident involving an armed man allowed in a lift with Mr Obama compounded calls for her to go.

"Today Julia Pierson, the Director of the United States Secret Service, offered her resignation, and I accepted it," Secretary of Homeland Security Jeh Johnson wrote in a statement.

"I salute her 30 years of distinguished service to the Secret Service and the Nation."

In the immediate aftermath of the security breach, the former head of the Secret Service, Julia Pierson, praised the officers on duty that night at the White House for their extraordinary restraint.

"Restraint?" some commentators and lawmakers have exclaimed in disbelief.

In the era of the suicide bomber is restraint really what you want when an intruder armed with a knife has penetrated into the inner sanctum of the leader of the free world?

Mr Obama also expressed his appreciation to Ms Pierson for her long history of public service, White House spokesman Josh Earnest told reporters on Wednesday.

Ms Pierson offered her resignation because "she believed it was in the best interests of the agency to which she has dedicated her career", Mr Earnest added.

In an interview with Bloomberg News after her resignation was announced, Ms Pierson said she knew Congress had "lost confidence in my ability to run the agency''.

Joseph Clancy, in charge of the presidential protective division of the agency, will take over as acting interim director.

High-ranking members of the US Congress had been calling for Ms Pierson's resignation in the wake of her testimony before a House oversight committee on Tuesday.