China's major Internet firms reported fast expansion in both revenue and R&D investment in the first five months, official data showed.

Chinese firms in the Internet and related sectors, whose business revenue exceeded 5 million yuan (729,927 U.S. dollars) last year, raked in 428.2 billion yuan from January to May, up 19.4 percent year on year, according to the Ministry of Industry and Information Technology.

R&D investment in the sector rose 15.6 percent year-on-year to 18.12 billion yuan in the period.

Information services, the biggest contributor, raked in 297.8 billion yuan during the period, up 21 percent than a year ago and making up 69.5 percent of the internet business revenue.

Key application infrastructure including Internet data centers, cloud services and cloud storage maintained rapid growth, as business revenue related to Internet data services came in at 4.13 billion yuan, up 36.5 percent.

Guangdong, Shanghai and Beijing, ranking top three in terms of Internet business revenue in the country, reported revenue growth of 12.2 percent, 25.3 percent and 19.5 percent respectively year-on-year in the first five months.