China's air force has carried out its first ever military drill over the western Pacific Ocean, state media said, highlighting Beijing's growing military reach.

Several aircraft from China's People's Liberation Army (PLA) on Monday flew over the ocean via the Bashi Channel, which runs between Taiwan and the Philippines, the official Xinhua news agency said.

"This is the first time that the PLA Air Force conducted such drills in an airspace far offshore from Chinese coastlines," Xinhua cited army spokesman Shen Jinke as saying.

The drill aimed to "level up the PLA Air Force's mobility and combativeness" over the "high seas", Xinhua reported.

Territorial tensions have increased in recent years between Beijing and its neighbours around the South China Sea -- which it claims almost in its entirety.

Beijing has also been building up its military reach in recent years, with its first aircraft carrier going into service in 2012.

China announced an 'Air Defence Identification Zone' (ADIZ) over the East China Sea in 2013, sparking condemnation from Japan and the United States.

Japanese media have reported that China is considering a similar zone over the South China Sea, which would be likely to further fan tensions in the region.

China has increased its military budget by double digit amounts for several decades, but says the spending is purely defensive and not aimed at other countries.

Several southeast Asian nations as well as Japan have boosted their defence budgets and ties with the US, in moves widely seen as reflecting fears about China.

The Bashi channel is a waterway between the Philippines' northernmost province of Batanes and Taiwan's Orchid island. Its ownership is disputed.

"The drill is not targeted at any certain country or targets and carries no threat against other countries and regions," Xinhua cited Shen as saying.