The head of the US government's personnel office resigned abruptly on Friday, giving in to bipartisan calls for her to step down following a government data breach that is believed to be the biggest in US history.

Katherine Archuleta, director of the federal Office of Personnel Management, submitted her resignation to President Barack Obama on Friday morning, the White House said.

That comes a day after the Obama administration said hackers stole Social Security identification numbers and other highly sensitive data from more than 21 million people.

Archuleta will be replaced on a temporary basis by the agency's deputy director, Beth Cobert, who will step into the role on Saturday.

Archuleta had earlier rebuffed demands to resign, telling reporters on Thursday she had no intention of leaving and that her agency was doing everything it could to address concerns about the safety of data in its hands.

But on Friday morning, Archuleta told Obama it was best to let new leadership respond to the recent breaches and to improve systems to lessen risks in the future, according to a White House official who was not authorised to be quoted on the matter and spoke on condition of anonymity.

On Thursday, within hours of the Obama administration releasing new details about the scope of the breach, House Republican leaders demanded new leadership in the agency, and a number of Democrats followed.

Among the data the hackers stole: criminal, financial, health, employment and residency histories, as well as information about their families and acquaintances.

Yet the government has insisted there were no indications that the hackers have used the data they stole.

Numerous US lawmakers have said China was behind the attack. But Michael Daniel, President Barack Obama's cybersecurity coordinator, said on Thursday the government wasn't yet ready to say who was responsible.

China has publicly denied involvement in the break-in.

Source: Agencies