The Apple News app, which the company announced in June, is available only to users in the United States, though it is being tested in Britain and Australia. Customers who already downloaded the app by registering their phones in the United States can still see content in it when they travel overseas — but they have found that it does not work in China.

Those in China who look at the top of the Apple News feed, which would normally display a list of selected articles based on a user's preferred media, instead see an error message: "Can't refresh right now. News isn't supported in your current region."

Apple, based in Cupertino, Calif., declined to comment.

Greater China is now Apple's second-largest source of revenue after the United States, with sales of more than $13 billion in the third quarter. That means the company is most likely taking a careful approach to delivering new content, like that on its news app, within China.