HONG KONG— Facebook Inc. is blocked in China, but Beijing is a big user of the platform to spread its political views to hundreds of millions of people overseas, sometimes via advertisements.

Now, some Facebook staff are raising concerns on internal message boards and in other employee discussions that the company is being used as a conduit for state propaganda, highlighting sponsored posts from Chinese organizations that purport to show Muslim ethnic minority Uyghurs thriving in China’s Xinjiang region, according to people familiar with the matter.

The U.S. and some European governments say Beijing is committing genocide against the Uyghurs, citing a campaign that includes political indoctrination, mass internment and forced sterilizations.

Facebook hasn’t determined whether to act on the concerns, say people familiar with the matter. The company is watching how international organizations such as the United Nations respond to the situation in Xinjiang, one of the people said. The U.N. this week called on firms conducting Xinjiang-linked business to undertake “meaningful human rights due diligence” on their operations.

A Facebook spokesman said that the ads taken out by Beijing pertaining to Xinjiang don’t violate current policies so long as the advertisers follow Facebook’s rules when purchasing them. He said the company is monitoring reports of the situation in Xinjiang “to help inform our approach and due diligence on this issue.”