SHANGHAI (Reuters) - China's largest e-commerce company Alibaba Group is planning to buy a stake in Sina Corp's Weibo, the nation's most popular microblogging service, China Business News reported on Monday. Alibaba declined to comment on the report. Sources in Alibaba told the official newspaper, which is owned by the Shanghai municipal government, that investment negotiations between Alibaba and Sina have entered the final phase. Alibaba has valued Sina Weibo at around $3 billion, the sources said. ...{br}{br}View the Entire Article{br}