Seeking damages and unspecified relief for harm caused, the U.S. Department of Housing and Urban Development said here in its civil charge that Facebook also restricted who could see housing-related ads based on national origin, religion, familial status, sex and disability.

Facebook said it had been working with the department to address the concerns and was surprised by the decision to issue the charge, having taken "significant steps" to prevent ads that discriminate across its platforms.

The company also said the government had "insisted on access to sensitive information - like user data - without adequate safeguards," adding that it was willing to provide aggregate reports but not user-level personal information.

The Housing Department claims Facebook mines data about its users and then employs machine learning to predict their responses to ads in ways that may recreate groupings defined by characteristics such as race.