BEIJING - China's top economic planner on Wednesday stressed the importance of boosting investment in the fourth quarter of 2015.

Increasing investment and stabilizing growth are priorities for the fourth quarter, according to a statement by the National Development and Reform Commission (NDRC).

Investment projects planned for the next year under the central budgetary management will begin before the end of this year, the NDRC said.

Construction of important national strategic projects, including the Belt and Road Initiative, the Beijing-Tianjin-Hebei integration plans and the Yangtze River Economic Belt, will receive enhanced support in the next three months, according to the statement.

The commission also stressed supporting major construction and investment projects listed in the proposals unveiled Tuesday on formulating the country's 13th five-year plan (2016-2020), as well as accelerating urbanization.

Collaborative projects between governments and private companies mainly funded and operated by the latter, or private-partnership (PPP) projects, will be supported and encouraged, the NDRC said.

The Chinese economy expanded 6.9 percent year on year in the first three quarters, marking a six-year low and the first time the quarterly growth rate has dropped under 7 percent since the second quarter of 2009.

With the economy slowing, China has underscored investment as a major tool to shore up growth.

The country's fixed-asset investment increased 10.3 percent year on year in the first nine months, 5.8 percentage points lower than the same period last year, official data showed.

Spending in infrastructure construction played a stabilizer role for the economy, with investment jumping 18.1 percent year on year during the first three quarters, up 7.1 percentage points from last year, and contributing about 29 percent of the overall investment.