Matsu Islands which officially belongs to Fujian Province's Lianjiang County - yes, officially according to the governments of both China and Taiwan, but controlled by Taiwan ever since the Chinese Civil War.
The Local Govt HQ. it says Govt of Lianjiang County, Fujian Province. Well, it's the govt-in-exile aka Taiwanese controlled. The Lianjiang county on the Mainland has a population of 600,000 while the Taiwanese controlled county on Matsu Islands has only 9,900 inhabitants.