SHANGHAI, CHINA: Microsoft said on Thursday its vice-president of sales for its MSN China joint venture would leave the firm at the end of March to pursue his own start-up.

Xiao Chen, who has been with the company since its inception in China, submitted his letter of resignation recently, a Microsoft spokeswoman told Reuters.

MSN China, which was launched in 2005 with local partners, ran into trouble late last year when its microblogging site, Juku --created by an independent vendor-- was accused of copying another start-up. Microsoft subsequently suspended the service.

China has the world's largest Internet market by users at 384 million at the end of last year.