Chinese government hackers breached the U.S. Treasury office that administers economic sanctions, the Washington Post reported on Wednesday, identifying targets of a cyberattack Treasury disclosed earlier this week.

Citing unnamed U.S. officials, the Washington Post said hackers compromised the Office of Foreign Assets Control and the Office of Financial Research and also targeted the office of U.S. Treasury Secretary Janet Yellen.

The department earlier this week disclosed in a letter to lawmakers that hackers stole unclassified documents in a “major incident.” It did not specify which users or departments were affected.

Asked about the paper’s report, Liu Pengyu, spokesperson for the Chinese Embassy in Washington, said the “irrational” U.S. claim was “without any factual basis” and represented “smear attacks” against Beijing.

The statement said China “combats all forms of cyberattacks” and did not directly address the Washington Post’s reporting on specific targets.

The Treasury Department did not immediately respond to requests for comment on the newspaper report.

The Washington Post quoted its sources as saying that a top area of interest for the Chinese government would be Chinese entities that the U.S. government may be considering designating for financial sanctions.

The Treasury letter earlier this week said hackers compromised third-party cybersecurity service provider BeyondTrust.

Chinese firms, individuals and entities have been a frequent target for U.S. sanctions, which Washington has used as a key tool in its foreign policy towards Beijing.

The United States considers China’s its biggest foreign policy challenge, and last month Yellen told Reuters that Washington would not rule out sanctions on Chinese banks as it seeks to reduce Russia’s oil revenue and access to foreign supplies to fuel its war in Ukraine.