Beijing dismissed concerns Thursday over recent reports of Chinese military aircraft manoeuvres near Japanese territory and in the South China Sea, state media said, calling them routine exercises.

Chinese planes recently passed through the Miyako Strait between Japan's Miyako and Okinawa Islands, China's defence ministry said in a statement on its website Saturday.

In a separate incident, US broadcaster Fox News reported last week that a Chinese bomber circumnavigated a disputed area of the South China Sea, a move seen as a message to US president-elect Donald Trump who has attacked Beijing's actions in the region.

China insists on sovereignty over virtually all the resource-rich waters, despite rival claims from its Southeast Asian neighbours.

The flights were "routine", Chinese Air Force spokesman Shen Jinke said, according to the official Xinhua news service.

"The overflight is about the mission and responsibility of the Chinese Air Force, and is legitimate, reasonable and justified," it reported him as saying.

"The Air Force will continue to conduct regular high sea drills and further improve its capabilities in safeguarding national sovereignty, security and development interests."

Chinese officials on Sunday accused Japanese fighter jets of firing flares at China's planes as they passed through international airspace near Japan's islands.

But Japanese officials denied the accusations, describing them as "clearly untrue".

The strait is a pinch point in Japan-China relations because it is one of the few egresses into the Pacific Ocean for Chinese ships and aircraft that avoid Japanese airspace.

Beijing's growing military is keen to flex its muscles and push further afield as it develops a "blue water" navy capable of operating far from home waters, but is hemmed in by the Japanese archipelago.

It is also eager to show its strength in the South China Sea, where the US claims its activities threaten freedom of navigation and overflight.

Last week, Trump blasted Beijing's South China Sea policy on Twitter, criticising its decision to build what he described as a "massive military complex" there.

Newly released satellite imagery shows China has apparently installed "significant" defensive weapons on a series of artificial islands in the region.