One of China's most successful Internet entrepreneurs, Jack Ma, founder of e-commerce giant Alibaba Group, says he is stepping down as chief executive but will remain chairman.

Ma said in a letter to employees on Tuesday that he would no longer be CEO after May 10 but would remain active as executive chairman of Alibaba Group. The company's business-to-business Alibaba and consumer-oriented Taobao and Tmall platforms are among the world's busiest e-commerce outlets.

Ma, a former English teacher, founded Alibaba in 1999. The Hurun Report, which follows China's wealthy, estimated his net worth last year at $2.4 billion.

Ma's letter said his successor as CEO would be named by May 10 but gave no indication who it might be.