China sent its first aircraft carrier into formal service on Tuesday amid a tense maritime dispute with Japan, a show of naval force that could worry its neighbors.

China's Ministry of Defense said the newly named Liaoning aircraft carrier would "raise the overall operational strength of the Chinese navy" and help Beijing to "effectively protect national sovereignty, security and development interests".

In fact, the aircraft carrier, refitted from a ship bought from Ukraine, will have a limited role, mostly for training and testing ahead of the possible launch of China's first domestically built carriers after 2015, analysts say.

But China cast the formal handing over of the carrier to its navy as a triumphant show of national strength -- at a time of bitter tensions with neighboring Japan over islands claimed by both sides.

Sino-Japanese relations deteriorated sharply this month after Japan bought the East China Sea islands, called Senkaku in Japan and Diaoyu in China, from their private owner, sparking anti-Japan protests across China.

"China will never tolerate any bilateral actions by Japan that harm Chinese territorial sovereignty," Vice Foreign Minister Zhang Zhijun said on Tuesday. "Japan must banish illusions, undertake searching reflection and use concrete actions to amend its errors, returning to the consensus and understandings reached between our two countries' leaders."

The risks of military confrontation are scant, but political tensions between Asia's two biggest economies could fester.

For the Chinese navy, the addition of carriers has been a priority as it builds a force capable of deploying far from the Chinese mainland.