BEIJING — In China, where Western-owned online services like Facebook and Google have long been blocked, Apple’s app store is a lucrative exception. Apple offers gaming, dining and dating apps in a country where most rivals are locally owned — and where it can reap big fees from iPhone users.

That business is now facing a number of threats.

The latest came this week, when a law firm representing more than two dozen app developers asked the Chinese authorities to investigate whether Apple’s app store policies violated local pricing and antitrust laws.

While it is not clear whether the government will respond, the call follows several other developments that have put a spotlight on the software and content that Apple offers in China. They include tighter regulations from the country’s censors and a high-profile public spat with a powerful and deeply connected Chinese internet giant, Tencent Holdings.

The challenges point to Apple’s difficulties in China, which is a major market for the company. Sales in China have fallen as customers wait for new iPhones and as domestic rivals make bigger and better devices. Apple, in response, has shifted its strategy to become increasingly dependent on services instead of hardware sales, making it more vulnerable to the whims of Chinese regulators.