China's biggest maritime drills in years involve around 60 warships and 30 coast guard vessels, stretching from the southern islands of Japan to the South China Sea, the senior national security official told AFP on the condition of anonymity.

Plans for the massive exercises began in October and were aimed at showing China could choke off Taiwan and also to "draw a red line" ahead of the next US administration.

"The real objective appears to be asserting control within the first island chain and establishing strategic deterrence ahead of the US presidential transition," the official said.

There has been no announcement by Beijing's People's Liberation Army or Chinese state media about increased military activity in the East China Sea, Taiwan Strait, South China Sea or Western Pacific Ocean, where Taiwan said Chinese ships had been detected.

However, a Beijing foreign ministry spokeswoman said Tuesday that China will "resolutely defend" its sovereignty.