China's first domestically designed aircraft carrier (File photo)

China's first domestically designed aircraft carrier embarked on its second sea trial on Monday from its shipyard in Dalian, Liaoning province.

Videos and images published by Chinese media and weapons enthusiasts showed that the giant ship, which has yet to be officially named but is widely believed to bear the name CNS Shandong, left the port of Dalian Shipbuilding Industry, its builder, assisted by several tugboats.

There appeared to be no aircraft or other large equipment on the vessel's deck.

Publicity officials from the People's Liberation Army Navy and China Shipbuilding Industry Corp, parent company of the Dalian shipbuilder, declined to comment.

The new carrier, the largest and most sophisticated naval vessel in China, was designed and built domestically, with construction beginning in November 2013. The ship was moved from dry dock to the water in April last year. It made its maiden sea trial in mid-May to demonstrate the reliability and performance of its propulsion systems.

A ship researcher from the Navy who asked not to be named said he expected the second sea trial to mainly verify the carrier's communication, navigation and other electronic and mechanical instruments.

He also said the operation will test modifications and improvements on the ship's propulsion system that were made after the first sea trial.

The ship still requires several sea trials before being commissioned by the Navy, according to the researcher.

The PLA Navy now operates just one carrier－the CNS Liaoning, originally a Soviet-era vessel that was extensively refitted by the Dalian shipbuilder. The vessel underwent 10 sea trials starting in August 2011 before entering service in September 2012.

The new carrier displaces at least 50,000 metric tons of water. It has conventional propulsion systems and will use a ramp to launch J-15 fighter jets, the spearhead of a Chinese carrier battle group, similar to the Liaoning. The ship will also carry several types of helicopters.

The first of China's Type 055-class guided-missile destroyers－Asia's largest and mightiest noncarrier warship－also started its first sea trial on Friday from Jiangnan Shipyard in Shanghai, according to witnesses. The vessel was launched in June 2017.

The Type 055 destroyer displaces more than 10,000 tons and has 112 vertical launching cells capable of firing various kinds of missiles, including the nation's long-range land-attack cruise missile.

Four Type 055s are under construction or in testing.