BEIJING, Dec. 11 -- China has doubled its number of state oil reserve silos to eight and almost doubled their capacity in less than a year as it bids to offset oil supply risks.

The country had built eight such silos as of mid-2015, with a total storage capacity of 28.6 million cubic meters, according to a press release issued by the National Bureau of Statistics (NBS) on Friday.

In November 2014, the NBS said four silos were in operation, capable of storing 16.4 million cubic meters of oil.

As of mid-2015, 26.1 million tonnes of crude oil were actually stored in the eight silos and non-state storage facilities, according to the NBS.

The eight are located in east China's Zhejiang Province, northeast China's Liaoning Province, east China's Shandong Province, north China's Tianjin City, and the northwestern Xinjiang Uygur Autonomous Region and Gansu Province.

The State Strategic Oil Reserve Base Program was launched in 2004 to reduce the impact of fluctuating energy prices worldwide on the domestic market for refined oil.

China is one of the world's largest oil buyers, importing nearly 60 percent of what it uses.

The government plans to build up oil reserves amounting to the equivalent of 100 days of net imports by 2020.