The White House says it has taken measures to counter suspicious activity detected on its unclassified computer network.
A White House official would not say who might have been responsible for the activity on what was described as an unclassified computer network used by employees of the Executive Office of the President.
The official, who spoke on condition of anonymity, said the authorities had taken "immediate measures to evaluate and mitigate the activity."
In a report on October 28, the "Washington Post" cited sources as saying hackers believed to be working for the Russian government breached the unclassified computer network in recent weeks.
The White House has declined to comment on the "Washington Post" report.
A U.S. administration official said there were no indications that classified networks had been affected.
Based on reporting by Reuters, AP, and dpa