China's defence ministry on Thursday said that military drills in southeast coastal regions were having an impact on civil aviation amid recent reports of widespread flight delays.

"It's a reality that military exercises will affect flights, and that's the case in all countries," ministry spokesman Geng Yansheng told reporters at a regular briefing.

China is holding military exercises across several provinces from July to October, state media have previously reported.

China's military controls much of the country's airspace -- some estimates say as little as 20 percent is reserved for civil flights. Industry officials say that results in longer flight times, less efficient routes and unaccountable delays.

Geng's comments came after China's civil aviation authority confirmed the exercises have been behind widespread flight delays and cancellations during July.

The Civil Aviation Administration of China (CAAC) said in a statement last week that "routine" military drills had impacted flights in the latter part of July, though it also cited weather and unspecified other reasons.

Cities affected included Shanghai, Nanjing and Qingdao in the east, and Wuhan and Zhengzhou in central China, the CAAC statement said.