Responding to a report in a German magazine that Chinese cyber spies stole sensitive data on defense programs, such as the United States' F-35 Lightning II fighter jet, China's Foreign Ministry spokesman Hong Lei said on Monday that such allegations are "totally groundless and unproven".

Such baseless accusations are not new for China, which itself has been at the receiving end of cyberattacks. Chinese cyber-spying might have increased the cost of the F-35 Joint Strike Fighter's and delayed its production, said Aviation Week, a New York-based information and services provider specializing in aerospace and intelligence, in 2012.

These allegations are being leveled at China to "prove" that it "stole" data on the US fighter jet to develop its own Chengdu J-20 and Shenyang J-31.