Chinese hackers accused of attacking US federal databases may have snared the names of Chinese with links to American officials, putting them in danger, The New York Times said.

Last week, the US government admitted hackers accessed the personal data of at least four million current and former federal employees, in a vast cyberattack suspected to have originated in China.

Investigators say that the hackers who breached the databases of the Office of Personnel Management could have obtained the names of Chinese relatives, friends and associates of American diplomats and other government officials, the Times said.

Beijing -- which labeled claims of Chinese involvement in the huge hack "irresponsible" -- could use that information for blackmail or retaliation, the newspaper said.

Federal employees involved with national security information are required to list some or all of their foreign contacts to receive high-level clearance, the report said.

According to the Times, intelligence officials have in recent days described in classified briefings to members of Congress "what appears to be a systematic Chinese effort to build databases that explain the inner workings of the US government," the newspaper said.

"It gives the Chinese the ability to exploit who is listed as a foreign contact," James Lewis, a cyberexpert at the Center for Strategic and International Studies, told the Times.

"And if you are a Chinese person who didn’t report your contacts or relationships with an American, you may have a problem."

The breach at the Office of Personnel Management was just the latest in a series of major incursions that have shown the vulnerability of the US federal government.