The government of the southern African nation of Zimbabwe detained, interrogated and deported officials and contractors working for the United States government last month, and this week accused them publicly of promoting “regime change” in their country.

The incident is the latest in the Zimbabwean government’s aggressive efforts to thwart both domestic and international challenges to its authority. The incumbent government claimed victory in a chaotic election last year that several independent observer missions said lacked fairness and credibility.

But it also points to a deeper tension over the United States’ proclaimed efforts to promote democracy around the globe. Some nations, including Zimbabwe, have accused America of meddling in their affairs and attempting to impose its values — as well as of hypocrisy, given the threats at home to its own democracy.

Leaders in Zimbabwe have grown closer in recent years to both China and to Russia, and have supported Russia’s invasion of Ukraine.

Zimbabwe sits on a wealth of lithium, a critical component in electric vehicles. But most Zimbabweans struggle to get by, coping with triple-digit inflation that has made their currency practically worthless. Many workers — both laborers and educated professionals — have left the country.

In a stern statement issued on Friday, Samantha Power, the administrator of the United States Agency for International Development, said that last month, the Zimbabwean authorities verbally and physically intimidated U.S. government officials and contractors. They were detained overnight, interrogated at length and transported in unsafe conditions, Ms. Power said.