BEIJING - China's top economic planner approved the construction of eight infrastructure projects, with an estimated total investment of 95.3 billion yuan ($15 billion), it announced Thursday.

The National Development and Reform Commission (NDRC) authorized plans to build two railways, one in Xinjiang Uygur Autonomous Region in the northwest and the other linking southwest China's Guizhou Province and central China's Hunan Province.

The agency also approved plans to build highways in Gansu, Hebei and Jiangxi provinces, construct two highway bridges across the Yangtze River and dredge part of the Grand Canal between Beijing and the eastern city of Hangzhou.

The most costly of the projects would be a 244-km expressway in northwest China's Gansu Province, expected to require 37.05 billion yuan.

Earlier this week, the NDRC said it had approved construction of four new railways stretching 2,000 km in total, with total investment of 253.3 billion yuan.

With its economy slowing, China has underscored spending on infrastructure as a major tool to shore up growth.

The NDRC approved 218 projects in fixed-asset investment in the first nine months of 2015, with investment adding up to 1.8 trillion yuan, NDRC secretary general Li Pumin told a press conference on Thursday.

Of the total investment, nearly 1 trillion yuan will go to transportation infrastructure. The rest will be spent on agriculture, energy, social programs, as well as high-tech and information technology industries.

Those investment will not only stimulate growth but also address some weak links of the economy and lay a solid foundation for long-term development, Li said.

China's fixed-asset investment increased 10.9 percent year on year in the first eight months, while investment in infrastructure jumped 18.4 percent, official data showed.