The prototype plane dubbed the J-20 flew for about 15 minutes over an airfield in the southwestern city of Chengdu where it was spotted carrying out runway tests last week, Kanwa Asian Defense magazine editor Andrei Chang said.
Photos of the plane in flight and on the ground surrounded by men in civilian clothes and army overcoats were also posted on unofficial Chinese military websites. A J-10 fighter - China's last homegrown jet - flew behind it as a chase plane.
The test flight comes on the second day of a visit to China by U.S. Defense Secretary Robert Gates, and the normally secretive military made no attempt to hide it or remove photos and reports about the J-20 from the Internet.
The timing and hands-off approach is apparently intended to send the message that Beijing is responding to calls from the U.S. and others to be more transparent about its defense modernization and future intentions.
Although likely many years from entering China's inventory, the J-20 is a potential rival to the U.S. F-22 Raptor, the only stealth fighter currently in service. The U.S. is also employing stealth technology on the F-35 Joint Strike Fighter, while Russia's Sukhoi T-50's stealth fighter made its maiden flight last year and is set to enter service in about four years.
In the photos, China's twin-engine J-20 appears larger than either the Russian or U.S. fighters, potentially allowing it fly farther and carry heavier weapons.
The J-20 would pose the greatest immediate threat to Taiwan, the self-governing island that Beijing claims as Chinese territory - to be recovered by force if necessary. Taiwan's air force is composed mostly of aging U.S. F-16s and French Mirage jets, and its electronic warning systems would find it difficult to cope with stealth technology.
A Chinese stealth fighter would "seriously undermine the Taiwan air force's advantages," said Alexander Huang of Taipei's Tamkang University.
While a state newspaper reported last week on the plane's appearance, China's government and military have yet to comment officially. People who answered phones at government and Communist Party offices in Chengdu, as well as the plane's developer - the Chengdu Aircraft Industrial Group - all refused to comment.
China's aviation industry - both military and civilian - has made rapid progress in recent years but still relies heavily on imported technology. Propulsion has been a special problem, with Russian engines still powering the J-10 and J-11, a copy of Russia's Su-27 fighter.
Stealth technology is even more difficult to master because it relies on systems to hide the presence of the plane, while equipping the pilot with enough information to attack an enemy. Emissions must be hidden and the plane's fuselage sculpted to avoid detection by radar and infrared sensors.
Despite the challenges, the J-20's entry into the test flight stage seems to indicate China is progressing faster than expected with the new technology, even while the plane's true capabilities aren't known. Analysts said two prototypes have been developed, with one employing a Russian engine and the other a Chinese one.
Chang said the Chinese engine-equipped prototype flew in Tuesday's test. "They're investing a lot to speed up development. You could call this a success," he said.
Chinese progress also potentially calls into question Gates' decision to cap production of the F-22 at 187 planes, partly because of claims that China would not have a fifth-generation fighter for years to come.
Along with the J-20, China's military is developing sophisticated new warships, submarines, missiles and possibly one or more aircraft carriers.
The military-backed space program has also conducted three manned flights, making China only the third country in the world to put a person into space.