Earlier J-20 which was displayed at China's biggest air show at Zhuhai last November made waves in India when its photographs at an airport in Tibet were published.
In a newscast on state broadcaster CCTV's military and agricultural affairs channel, an announcer said in a brief statement that the J-20 had "entered" service in the country's airforce.
The J-20 stealth fighters are created to compete with other fifth generation fighter jets, such as the F-22 Raptor of the United States and the Russian PAK-FA. The closest look alike of the J-20 is the F-22, developed for the U.S. Air Force.
Wang Weiming, the deputy chief of staff of the People's Liberation Army Navy, said China was speeding up the development of its marine corps, adding destroyers and frigates, to step up air and sea patrols in its territories.
"We will intercept any intruding aircraft and follow every military vessel in areas under our responsibility", Wang said.
The navy is another key focus for China.
According to Reuters, the Chinese navy has been playing an active role in recent months with its first aircraft carrier sailing around Taiwan.
China is also focusing on the development of its navy, though its offensive punch, is as yet, limited by the presence of only one aircraft carrier, which is mainly used for training purposes. It is expected to be in service sometime in 2020 and will join the existing carrier Liaoning.
Navy arms manufacturing would have "better quantity, quality, scope, and functionality", Li said, without elaborating.
China's regional neighbors have been unnerved by its more aggressive stance in the South China Sea, with Beijing increasing defense spending and building artificial islands that are reportedly outfitted with weapons.
China this year initially failed to publicly release its defence budget on the opening day of parliament as it has done in previous years, finally saying a day later on Monday that it would rise by 7 percent to 1.044 trillion yuan ($151.12 billion).
Swift, stealthy, and armed with long-range missiles, the J-20 represents a leap forward in China's ability to project power in Asia and potentially compete with the United States.
China also recently sent its first aircraft carrier, an overhauled Ukrainian ship, for a debut voyage into the Pacific.
Deputy political commissar of the Eastern Theatre Command, Wang Huayong, said that the forces are exclusively for defensive purposes.