China's first aircraft carrier completes South China Sea drills BEIJING (Reuters) - China's first aircraft carrier has successfully finished a series of tests during a training mission in the disputed South China Sea and has returned to port, state media reported. Last month's drills off the coast of Hainan Island marked not only the first time China has sent a carrier into the South China Sea but the first time it has maneuvered with the kind of strike group of escort ships U.S. carriers deploy, according to regional military officers and analysts. After two decades of double-digit increases in the military budget, China's admirals plan to develop a full blue-water navy capable of defending growing economic interests as well as disputed territory in the South and East China Seas. The aircraft carrier Liaoning carried out more than 100 tests, including of its combat systems, and has now docked at port in the northern city of Qingdao, the official Xinhua news agency said late on Wednesday. "The aircraft carrier underwent a comprehensive test of its combat system and conducted a formation practice during its 37-day voyage," Xinhua said, citing an unnamed naval source as saying. The tests "attained the anticipated objectives," the report added. All tests and training programs went well as scheduled. The carrier was escorted by two destroyers and two frigates, and aircraft and submarines also participated in the drills. The Liaoning - a Soviet-era ship bought from Ukraine in 1998 and re-fitted in a Chinese shipyard - has long been a symbol of China's naval build-up. Carrier strike groups sit at the core of China's naval ambitions and successfully operating the 60,000-tonne Liaoning is the first step in what state media and some military experts believe will be the deployment of locally built carriers by 2020. Friction over the South China Sea has surged as China uses its growing naval might to assert a vast claim over the oil-and-gas-rich area, raising fears of a clash between it and other countries in the region, including the Philippines and Vietnam. The USS Cowpens narrowly avoided colliding with a Chinese warship escorting the Liaoning while operating in international waters on December 5, the U.S. Navy has said. Xinhua said the Cowpens was "warned" by the carrier task force, adding the U.S. vessel was "intentionally" putting the Liaoning under surveillance. Reporting by Ben Blanchard; Editing by Michael Perry