BEIJING (Reuters) - No amount of interference or shadowing of its aircraft will stop the Chinese air force from carrying out long-range drills, the defense ministry said, announcing another round of exercises of the type that have unnerved neighbouring Taiwan and Japan.

The air force carried out further long-range exercises on Thursday, the ministry said, without giving details of where they happened. Japan said it was concerned about bombers flying close to its territory.

Such “normal” drills accord with international law and practices and are part of an “ordinary need” to raise combat abilities and strengthen the military, it added.

“No matter what obstructions are encountered, the Chinese air force will carry on as before; no matter who flies with us, the Chinese air force will fly a lot and as normal!” the ministry added, citing an air force spokesman.

China has been increasingly asserting itself in territorial disputes in the South and East China Seas. It is also worried about self-ruled Taiwan, claimed by China as its own and run by a government Beijing fears is intent on independence.

Japan’s government said six Chinese bombers flying from the East China Sea on Thursday passed close to its islands on route to the Pacific Ocean.

It was the first time we have recorded Chinese military aircraft flying this route,” Minister of Defence Itsunori Onodera said during a regular press briefing on Friday. “We expressed our concern through diplomatic channels,” he added.

Drills over the past few months have mostly focused on flying near Taiwan and by Japan’s southern island chain to the north of Taiwan.

Taiwan’s military said earlier this month it was on a high state of alert following three straight days of drills by the Chinese air force near it.

Beijing has never ruled out the use of force to bring proudly democratic Taiwan under its control, and has warned that any moves towards formal independence could prompt an armed response.

Taiwan is well armed with mostly U.S. weaponry, but has been pressing Washington to sell it more high-tech equipment to better deter China.

China is in the midst of an ambitious military modernization program that includes building aircraft carriers and developing stealth fighters to give it the ability to project power far from its shores.

Separately, the official Xinhua news agency said on Friday that Chinese warships had carried out live fire drills in the western part of the Indian Ocean, though it did not say where exactly.

Chinese warships frequently pass through the Indian Ocean on their way to anti-piracy patrols in the waters off Somalia and Yemen.

India, with which China has a festering border dispute, has expressed concern about Chinese military activity in the Indian Ocean.