Washington, July 10 (IANS): A cyber attack on the US government, allegedly by Chinese hackers, was more severe than initial reports, affecting “sensitive” information of millions of people, the Obama administration has said.

The Office of Personnel Management -- victim of the attack that was exposed in June -- reported on Thursday that “hackers” robbed personal data, including social security numbers and other information of 21.5 million people, according to Efe news agency.

Of these, 19.7 million are people who had applied for jobs in administration or the government and other individuals linked to the public sector, on whom the government ran security checks.

The remaining 1.8 million are families of some of the above.

In addition to social security numbers, the hackers also accessed addresses, financial and health histories.

The 21.5 million affected also include people who were victims of another "separate, but related" cyber-attack, affecting 4.2 million current and former federal government employees.

The sum of all those affected by these attacks amount to around seven percent of the US population, making it one of the most damaging attacks ever recorded against the US administration, both in terms of the number affected and sensitivity of stolen data.

Although, there is no "scientific evidence", voices from US media and politics suspect a Chinese hand.

According to The Washington Post, "China is building massive databases of Americans' personal information", for "recruiting spies or gaining more information on an adversary".