Fresh reports that China is building a second aircraft carrier circulated over the weekend on a city government microblog and a state-owned newspaper, as the country scrambles to modernise its military.

China wants to develop an ocean-going "blue water" navy capable of defending the growing interests of the world's second largest economy as it adopts a more assertive stance in territorial disputes with neighbours in the South China and East China seas.

A power cable maker in the eastern city of Changzhou has won a deal to provide equipment for the second aircraft carrier, according to the reports, which appeared on the official microblog of the government of Changzhou and the state-backed Changzhou Evening News, but have since been deleted.

Chinese military analysts said the reports were a tacit acknowledgement the carrier was being built.

Media reports last year cited the top party official in the northern province of Liaoning as saying that China was building the carrier, and aimed for a future fleet of at least four aircraft carriers.

But the government has consistently sought to keep news about a second aircraft carrier quiet, and the military has not formally acknowledged its development.

The country's first aircraft carrier, the Liaoning, a Soviet-era ship bought from Ukraine in 1998 and refitted in a Chinese shipyard, has long been a symbol of China's naval build-up.

Successfully operating the 60,000-tonne Liaoning is the first step in what state media and some military experts believe will be the deployment of domestically-built carriers by 2020.