has announced plans to set up two new research and development centers in China amid continued challenges to the iPhone maker in the world's second-largest economy.

The U.S. technology titan said Friday that the hubs would be in Shanghai and Suzhou. This follows to open R&D centers in Beijing and Shenzhen.

Apple has committed to invest more than 3.5 billion yuan ($507.1 million) in research in China, the company said.