China's Dalian Wanda Group Co, whose real estate arm just raised about $3.7 billion in a Hong Kong share sale, said on Friday it has bought a controlling stake in 99Bill Corp, a Chinese third-party payment processor similar to PayPal.

China's biggest commercial property developer did not say how much it paid for the stake, which marks its first acquisition in the Internet finance sector, but sources familiar with the deal told Reuters it may have spent more than 2 billion yuan ($322.55 million).

The Beijing-based conglomerate is diversifying into e-commerce as it seeks to maintain profitability during China's property downturn.

"Wanda Group hopes that 99Bill will soon provide online payment solutions for all Wanda's businesses, and quickly become a leading payment and financial service provider in China," Ding Benxi, Dalian Wanda's chief executive, told a news conference.

The 99Bill tie-up places property billionaire Wang Jianlin, Dalian Wanda's chairman, into direct competition with Alibaba Group Holding Ltd Executive Chairman Jack Ma and his Alipay unit, which controls about 80 percent of China's mobile payment market.

Alipay settled $788 billion in transactions in the year ended on June 30.

Wang has said he was preparing to shift the focus of the conglomerate towards entertainment, tourism and online businesses. He said at a conference this month that he would announce plans for transforming the group early next year.

In August, Dalian Wanda teamed up with two Chinese Internet giants, Tencent Holdings Ltd and Baidu Inc, to launch an e-commerce joint venture that could leverage the group's 104 Wanda Plaza shopping malls, 72 luxury hotels and 150 movie theaters in 111 Chinese cities..

Dalian Wanda is investing 5 billion yuan and holds a 70 percent stake in the venture, which is promoting the use of e-vouchers, e-coupons and e-tickets at the group's properties.

"O2O (online to offline) is the biggest pie in e-commerce," said Wang. "This is just the beginning."