China's first domestically developed aircraft carrier has left its north-eastern port to begin sea trials, state media said — Beijing's latest milestone in efforts to modernise its military.

Key points: The trial is to test the reliability of equipment, state media said

The trial is to test the reliability of equipment, state media said The Tyoe 001A carrier is based on the Russian model

The Tyoe 001A carrier is based on the Russian model The sea trial comes as China continues military influence in South China Sea

The still-unnamed ship left dock in the northern port of Dalian at 7:00am, the Defence Ministry said in a statement.

The carrier was launched this time last year but since then has been undergoing weapons fitting and work on other systems and has not yet entered service.

The official Xinhua news agency confirmed the ship had left for trials with a short announcement.

"Our country's second aircraft carrier set sail from its dock in the Dalian shipyard for relevant waters to conduct a sea trial mission, mainly to inspect and verify the reliability and stability of mechanical systems and other equipment," Xinhua said.

Little is known about China's aircraft carrier programme, which is a state secret, though official media in recent weeks had widely speculated that sea trials were set to start.

Type 001A is China's first homemade aircraft carrier and will join China's only other carrier, Liaoning. ( Supplied: Weibo )

Chinese President Xi Jinping is overseeing an ambitious plan to update the armed forces, including the development of stealth jets and anti-satellite missiles, as China ramps up its presence in the disputed South China Sea and around self-ruled Taiwan, an island it considers its own.

Chinese military experts have told state media that the carrier is not expected to enter service until 2020, once it has been fully kitted out and armed.

But the government has said the new carrier's design draws on experiences from the country's first carrier, the Liaoning, bought second-hand from Ukraine in 1998 and refitted in China.

The new conventionally-powered carrier will be able to operate China's Shenyang J-15 fighter jets.

Unlike the US Navy's longer-range nuclear carriers, both of China's feature Soviet-design ski-jump bows, intended to give fighter jets enough lift to take off.

They lack the powerful catapult technology for launching aircraft that US carriers have.

China's navy has been taking an increasingly prominent role in recent months, with its first aircraft carrier, expected to serve more as a training vessel, sailing around self-ruled Taiwan and new Chinese warships popping up in far-flung places.

State media has quoted experts as saying that the country needs at least six carriers.

The US operates 10 and plans to build two more.

AP/Reuters