China says it is building second aircraft carrier

China on Thursday confirmed that it is building its second aircraft carrier.

Col. Yang Yujun, a spokesman from the Ministry of Defense, told reporters that the 50,000 ton China-designed vessel is being constructed in the northern port of Dalian with domestic technology.

"China has a long coast line and a vast maritime area under our jurisdiction," Yang said, according to Reuters. "To safeguard our maritime sovereignty, interests and rights is the sacred mission of the Chinese armed forces."

In February, officials in Changzhou, eastern China, said Jiangsu Shangshang Cable Group — a local company — won a contract to supply cabling for the carrier, but their comments were soon deleted from the internet.

Chinese media has published images appearing to show the development of the vessel. The country's aircraft carrier program is a state secret.

Obama turns up heat again on China's assertiveness in South China Sea

China's existing aircraft carrier, the Liaoning, isn't yet fully operational. In October, the Associated Press reported that 27 U.S. Navy personnel visited it, where they discussed issues including training.

Yang said work on the second carrier has drawn on China's experience refitting the Liaoning, which was purchased from Ukraine in 1998.

He said the new carrier will have a ski-jump take-off, unlike the the Liaoning, but did not say when it will enter service, according to Reuters.

China, which has included new frigates, destroyers and nuclear submarines in its naval fleet, claims territorial sovereignty to virtually all of the South China Sea, which includes some of the world's busiest trade routes. Five other countries have competing claims in the same region.

President Obama has repeatedly criticized China's military expansion in the area.