Apple Inc. will set up two new research and development centers in China, totaling the number to four, the company said in a statement on its Chinese website on Friday.

The new centers will be located in east China's Shanghai and Suzhou, in addition to the two previously announced ones in the capital, Beijing, and the southern coastal metropolis, Shenzhen.

The world's most profitable tech company has pledged to invest more than 3.5 billion yuan (roughly 500 million US dollars) in research and development in China.

The firm also promised to hire more local technicians, and have more cooperation with local tech companies, to develop "advanced tech and services for clients in China and the whole world."

Apple wants to sustain development in China, which requires more Chinese professionals from top universities in the country.

The four centers are expected to open later this year, it said.

Apple didn't perform so well in the Greater China region for the first fiscal quarter of 2017, with revenue going down 12 percent year-on-year to 16.2 billion US dollars, according to Apple CEO Tim Cook.

It's the only area that saw negative growth in the whole world.

Cook said a weak yuan is an important reason for the decline.

(With inputs from Reuters)