BEIJING, November 29, 2011 - China's first aircraft carrier began its second sea trial on Tuesday after undergoing refurbishment and testing, the government said.
The 300-metre (990-foot) ship, a refitted former Soviet carrier called the Varyag, underwent five days of trials in August that sparked international concern about China's widening naval reach.
"China's aircraft carrier platform, after successfully completing its first sea trial in August, returned to the shipyard as planned for further refitting and testing," the defence ministry said in a statement.
"The work has been carried out and it set sail again on November 29 to carry out relevant scientific and research experiments."
The announcement comes against a background of growing tensions over maritime disputes in the Asia-Pacific region.
China has become increasingly assertive in its claims over the East China Sea and South China Sea.
Last week Beijing said it would conduct "routine" naval exercises in the Pacific Ocean, following a major diplomatic campaign by US President Barack Obama to assert the United States as a Pacific power.
Beijing only confirmed this year that it was revamping the old Soviet ship and has repeatedly insisted that the carrier poses no threat to its neighbours and will be used mainly for training and research purposes.
But the August sea trials were met with concern from regional powers including Japan and the United States.