BEIJING, Aug. 23 (Xinhua) -- China's top economic planner announced on Tuesday that contracts for 619 public-private partnership (PPP) projects worth one trillion yuan (151 billion U.S. dollars) had been signed as of the end of July.

The projects include those in public infrastructure, railways and ports, according to the National Development and Reform Commission (NDRC).

PPPs are collaborative projects between governments and private companies that are mainly funded and operated by the latter.

Chinese authorities have explored funding infrastructure and public works through the PPP model since late 2013 amid growing concerns over rising local government debts incurred through local financing vehicles.

Since last May, the NDRC has announced two rounds of PPP projects worth 4.23 trillion yuan.

In September 2015, the Ministry of Finance started a fund with 180 billion yuan to support the financing of PPP projects.