A report by the Stockholm International Peace Research Institute (SIPRI) has hinted on China being world's second largest producer of munitions. The report notes however that the lack of transparency remains an "important caveat" when studying the Chinese arms industry.

Stockholm: The opaque Chinese arms industry has made the Asian nation the world's second largest producer of munitions, a clear shift from a decade ago when China relied on imports, researchers said in a new report Monday.

The report by the Stockholm International Peace Research Institute (SIPRI) suggests that China's weapons production, which has previously been shrouded in mystery owing to a lack of transparency, has grown as three of the world's top 10 arms companies are Chinese.

"We can with confidence say that China is the second largest arms producer in the world, behind the US and ahead of Russia," Nan Tian, co-author of the report, told AFP.

The report notes however that the lack of transparency remains an "important caveat" when studying the Chinese arms industry.

The vast majority of the estimated $70-$80 billion (63 to 72 billion euros) worth of Chinese munitions sold every year are bought by the different branches of China's People's Liberation Army (PLA).

This still represents a dramatic shift over the last 10 years as China in the past was a big importer of weapons from Russia and Ukraine.

"They no longer need to rely on other countries for their weapons," Tian said.

Chinese arms companies are also much more specialised than their international counterparts.

Aviation Industry Corporation of China (AVIC), the country's largest arms company, for instance, mostly produces aircraft and avionics, while most large non-Chinese producers cover a wide range of military products.

- 'Reasonably reliable estimates' - SIPRI researchers have previously struggled to obtain reliable data on the size of the Chinese arms industry, since the producers are all state-owned entities.

"Everything is locked under the term national security," Tian said.

In the report the researchers have looked into four specific Chinese companies, all of which rank among the world's top 20, and say that with an increase in the available data on these companies "it is now possible to develop reasonably reliable estimates of the scale of the Chinese arms industry."

Though there are no official statistics on Chinese arms exports available, the report notes that the Chinese arms "industry has developed to a point where there is an increased demand for its weapons overseas," and estimates place China as the world's fifth largest weapons exporter, SIPRI said.

In particular Tian said that one of China's success stories as a weapons exporter has been in the area of Unmanned Aerial Vehicles (UAV), commonly known as drones, which have been used in conflicts in both Libya and Yemen.

More arms exports increases the risk of weapons proliferation, but China's entry to the world stage of weaponry sales is of special concern to the researchers since Beijing has not signed on to many of the arms control regulations that exist, including the Arms Trade Treaty approved by the UN General Assembly in 2013.

"There is no binding system that can hold China and these exporters accountable," Tian said.