China's most advanced aircraft carrier, the Fujian, has entered service days after a grand commissioning ceremony overseen by Chinese leader Xi Jinping, state media said.

The Fujian is China's third aircraft carrier, with a flat flight deck and electromagnetic catapults for take-offs that make it a potentially far more powerful naval weapon than China's first two Russian-designed carriers.

The US is the only other country in the world to have an aircraft carrier with the same electromagnetic catapult system as Fujian.

The Fujian will be able to carry significantly more and heavier-armed jet fighters than the Liaoning and Shandong carriers.

Its launch marked a significant step forward for Beijing, which now has the world's largest navy in terms of sheer number of ships.

The carrier's crew stood in formation on the deck to bid farewell to Xi on Wednesday, chanting "obey the (Communist) Party's command, be able to fight and win, maintain exemplary conduct", state media reported.

China has been expanding its navy at breakneck speed under Xi, putting pressure on the United States and its allies to keep up.

The Fujian can launch three different types of aircraft, according to state media.