As Russia intensifies its assault on Ukraine, it is getting a helping hand from China in spreading inflammatory and unsubstantiated claims that the U.S. is financing biological weapons labs in Ukraine.

The U.S. has been quick to refute Russia’s conspiracy theory, and the United Nations has said it has received no information that would back up the claim, but that hasn’t stopped it from proliferating.

The partnership between the two authoritarian countries, which weeks ago said their ties had “no limits,” appears aimed at muddying the waters of the rationale for Russia’s invasion in what American officials have called an “information war” that some fear could lay the groundwork for a “false-flag” operation.

China’s Foreign Ministry has helped fuel the fire this week, repeating the Russian claim several times and calling for an investigation.

“This Russian military operation has uncovered the secret of the U.S. labs in Ukraine, and this is not something that can be dealt with in a perfunctory manner,” ministry spokesperson Zhao Lijian said Thursday.