Jack Ma, Executive Chairman of Alibaba Group, speaks at the WSJD Live conference in Laguna Beach, California October 27, 2014. [Photo/Agencies]

The founders of Alibaba Group Holding Ltd and Tencent Holdings Ltd were among a consortium of investors who purchased stakes in Ping An Insurance Group Co of China Ltd in a HK$36.5 billion ($4.7 billion) deal on Sunday, in one of the largest Hong Kong share offerings of the year.

Alibaba Executive Chairman Jack Ma was one of Ping An's new backers, according to a person familiar with the matter. Tencent Chairman Pony Ma also participated, according to domestic financial news magazine Caijing.

A Tencent spokeswoman was not available to comment. A Ping An spokeswoman could not be reached for comment.

The deal reinforces ties between China's second-largest insurance company and two Internet giants. The three firms collaborated previously, in 2013, to set up Zhong An Online Property Insurance, China's first online insurance seller.

Collectively known as the "Three Mas", the Alibaba and Tencent chairmen, along with Ping An chairman Ma Mingzhe also jointly invested in media production company Huayi Brothers Media Corp last month.

Shares of Alibaba fell 5 percent on Monday in their steepest one-day drop since their September listing. US retailers on the same day said Internet rivals such as Alibaba could "decimate" local companies unless Congress closes tax loopholes for online retailers.