China will auction about 30 oil and gas blocks in the northwestern region of Xinjiang this year to investors outside the top state energy firms as Beijing steps up efforts to boost private participation in the sector, state media reported,.

Lack of private investment in oil and gas exploration has been a big stumbling block in Beijing's attempts to reform the sector, and it has picked the hydrocarbon-rich autonomous region of Xinjiang to try to break the grip of the big companies.

China's top two energy giants, China National Petroleum Co. (CNPC) and Sinopec Group have been the dominant players onshore China, while China National Offshore Oil Co. (CNOOC) dominates offshore E&P.

This will be the second such auction in Xinjiang, this time covering 30 oil and gas exploration blocks totaling 300,000 square kilometers, or 115,830 square miles, Xinhua reported on July 21, citing Xinjiang's land and resources agency.

The blocks have been relinquished by the state-run oil giants, the report said, without providing further details.

In July 2015, the Ministry of Land and Resources released five blocks in Xinjiang in its first tender to attract non-state investors. An independent Shandong-based company and state-owned Beijing Energy Investment Holdings were among the firms awarded four of the five blocks, Reuters has reported.

Those companies had pledged to spend a total of nearly 8.5 billion yuan ($1.24 billion) over three years, the Xinhua report said.

(US$1 = 6.8498 Chinese yuan)