BEIJING - China's latest J-20 stealth fighters have been commissioned into air force combat service, a spokesperson confirmed Friday.

"It marks an important step for the J-20 to have comprehensive combat capabilities," said Shen Jinke, spokesman for the Chinese People's Liberation Army (PLA) Air Force.

Since the fighters have been commissioned into the combat units, the air force has made steady progress in the training of pilots, he said.

According to the spokesman, J-20 played a vital role in the air force's Red Sword 2017 exercise and laid a foundation for the enhancement of its new war capacities.

"The stealth jets will improve the air force's comprehensive fighting ability and enable it to better safeguard China's sovereignty, security and territorial integrity," Shen said.

The J-20 is China's fourth-generation medium and long-range fighter jet. It made its maiden flight in 2011 and was first shown to the public at the 11th Airshow China in Zhuhai, Guangdong province, in November 2016.

The fighters made their parade debut when the PLA marked its 90th anniversary in July 2017 at Zhurihe military training base in Inner Mongolia autonomous region.