Washington, June 11 (IANS/EFE): The massive cyber attack, which was revealed last week and which compromised information on up to four million US federal employees, sought data on Chinese citizens linked to the US, The New York Times (NYT) has reported.

The cyber attack was carried out by Chinese hackers -- yet to be confirmed officially -- looking for names of Chinese citizens who are "relatives, friends and frequent associates of American diplomats and other government officials", NYT said on Wednesday citing sources from the investigation.

According to the newspaper, Beijing could use this information for "blackmail or retaliation".

The attack on US Office of Personnel Management's computer system which occurred in December and was detected in May, could be the biggest information theft ever against the US.

Officially, there has been no confirmation of the perpetrators of the attack, however sections of the US media claim that Chinese hackers were behind it.

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

The Chinese government has said that there was no scientific evidence that linked them to the cyber attack.

Federal employees who handle sensitive information on US national security are required to provide a list of their foreign contacts.

The hackers were after these lists, which could have names of Chinese citizens.