BEIJING, June 13 -- China's estimated oil and natural gas reserves have risen markedly in the past few years as prospecting has increased, the latest official assessment showed.

Potential oil resources now reach 126 billion tonnes, with an extractable amount of 30 billion tonnes, the Ministry of Land and Resources announced Monday, citing results of a national assessment completed in 2015.

The numbers are up 64 percent and 42 percent, respectively, from the the last such assessment in 2007, the ministry said.

The country is estimated to have 90 trillion cubic meters of natural gas resources, 50 trillion of which can be exploited, up 158 percent and 127 percent from the last assessment.

The ministry attributed the growth to increased exploration and better technology.

China is thought to be rich in unconventional oil and gas resources, with 122 trillion cubic meters of shale gas no more than 4,500 meters underground, 22 trillion of which is exploitable, according to the ministry.