It is based on the former Soviet navy's unfinished Varyag, which was towed from Ukraine in 1998 minus its engines, weaponry and navigation systems.

Named "Liaoning" after the north-eastern province surrounding its home port of Dalian, the ship began sea trials last August following years of refurbishment.

So far the trial runs of the aircraft carrier have been to test the ship's communications, propulsion and navigation.

But launching and recovering fixed-wing aircraft at sea is a much trickier proposition.

Building the proper aircraft and training pilots to land in bad weather on a moving deck will take years, as will developing a proper carrier battle group.

Beijing has not said what role it intends the carrier to fill other than helping safeguard China's coastline and sea links. It has also been portrayed as a kind of test platform for the future development of up to five domestically-built Chinese carriers.

China's defence ministry's announcement of the launch had been long-expected and was not directly linked to current tensions with Japan over a disputed group of uninhabited East China Sea islands.

In a brief notice on its website, the ministry said: "It has important significance in effectively safeguarding national sovereignty, security, and development benefits, and advancing world peace and common development."

Retired Rear Adm Yang Yi said a strong Chinese navy would lead to a stable region.

Picture: AP/Xinhua