China has tested its first stealth combat drone, state media said on Friday, citing online photos of an aircraft resembling a shrunken US B2 bomber and hailing the advance toward Western-level technology.

The test flight of the "Sharp Sword" unmanned aircraft is another step in China's years-long military build-up, with its defence spending now the second highest in the world and growing by double-digit percentages each year.

It comes weeks after Tokyo said a drone had flown near East China Sea islands claimed by both it and Beijing, causing tensions between the rivals to escalate by another notch.

"The successful flight shows the nation has again narrowed the air-power disparity between itself and Western nations," the China Daily newspaper said.

It said Thursday's test flight made China the "fourth power... capable of putting a stealth drone into the sky", after the US, European Union and Britain.

Images posted online showed a sleek grey delta-wing aircraft apparently powered by a jet engine and resembling an American combat drone.

State media widely reported the new aircraft in close detail, although they said the test-flight was first revealed by ordinary Internet users on a popular military web forum cjdby.net.

Chinese authorities quickly censor any news or images exposed online by citizens that they deem sensitive, so it is unlikely they did not approve the reports.

State broadcaster CCTV, citing eyewitnesses, said on its international channel that the test flight lasted 20 minutes on Thursday afternoon in the southwestern city of Chengdu.

The flight "implies that China has made the leap from drones to combat drones", it said, calling it the move of "major significance".

The aircraft was developed by two subsidiaries of Aviation Industry Corp of China, the country's top aircraft manufacturer, the China Daily said.

China is steadily building its military muscle and unveiled its first stealth fighter, the J-20, in early 2011, though it is not expected to to enter service until 2018.

Beijing's first aircraft carrier -- a refurbished vessel purchased from Ukraine and named the Liaoning -- went into service in September 2012 but is not expected to be fully operational for several years.

A drone was at the centre of a recent spat between Beijing and Tokyo, whose dispute over islands known as Diaoyu in Chinese and Senkaku in Japanese has raised concerns of conflict.

An unidentified unmanned aircraft flew near the islands in September, where China routinely conducts maritime patrols, prompting Japan to scramble fighter jets. The aircraft came from the northwest and returned in that direction, a Japanese defence official said.

Tokyo later threatened to shoot down any such aircraft, a move that Beijing warned would amount to an "act of war".