It's being reported China's sovereign wealth fund has invested an unspecified amount in taxi-booking app Didi Kuaidi.

China Investment Corporation is said to be one of several investors that has injected more than 2-billion U.S. dollars in recent months into the app, which is now valued at around 15-billion U.S. dollars.

The size of CIC's investment has not been revealed.

CIC currently has around 600-billion U.S. dollars under management, including holdings in overseas real estate, natural resources and Chinese e-commerce giant Alibaba.

Didi Kuaidi controls 80 percent of China's private taxi-hailing market.

The startup's other backers include Alibaba, Tencent, Coatue Management and Singaporean state investment firm Temasek Holdings.