China's first aircraft carrier started sea trials Wednesday, a step that will likely boost concerns about the country's naval ambitions amid sea territorial disputes.

The carrier left Dalian port in northeast Liaoning province early Wednesday, the official Xinhua News Agency reported. The test run had been expected.

Xinhua said the first sea trial was in line with the schedule to rebuild the carrier, which China bought from Ukraine more than a decade ago. The report cited unnamed military sources.

China officially acknowledged only two weeks ago that it is rebuilding the carrier and said the refurbished ship would be used for research and training _ a strong indication it plans to build carriers of its own.

China's carrier ambitions have sparked concern among neighbors amid heightened tensions over territorial disputes around Taiwan and in the South China Sea.

Over the past year, China has seen a flare-up in territorial spats with Japan, the Philippines and Vietnam and seen its relations strained with South Korea _ all of which have turned to Washington, long the pre-eminent naval power in Asia, for support.

Xinhua said refitting and test work would continue on the carrier when it returns from its short sea trial.

The Varyag, yet to be officially renamed, was towed from Ukraine as an empty shell without engines, weapons systems or other crucial equipment. It has been under construction for the better part of a decade.

Defense experts say China plans up to four carriers in all, with preparations under way at a Shanghai shipyard.

No time period for the trial was given by Xinhua, but a statement posted on the website of the Liaoning Maritime Safety Authority said "all vessels will be barred from entering" a small section of the sea off Dalian until 6 p.m. (1000 GMT) on Aug. 14.

There had been earlier online reports in China that the test was set to start last weekend, but it may have been delayed by a tropical storm that swept through the area.

