China's first aircraft carrier, Varyag, has concluded its four-day sea trial and sailed back to the Dalian port.

Varyag, which attracted worldwide attention in the backdrop of fears that the second-largest economic powerhouse is rapidly bolstering its military powers, will undergo more refitting at the Dalian port, Xinhua news agency reported.

The aircraft carrier's flight deck and the radar system could be spotted when it was pulled back by seven tugboats into the port, but weapon systems were covered under sheets, the report said. It said authorities haven't revealed what weapons are installed on the aircraft carrier, which is refitted from a former Soviet Union vessel.

The carrier was built by the Russians, but was left incomplete following the disintegration of the former USSR. It was sold to Ukraine in the 1990s as an empty hull and China later bought it.

All major maritime powers have aircraft carriers, which are gigantic moving battle platforms, and China's debut in this arena is belated.

Earlier, a Xinhua commentary said contrary to popular perception, acquisition of an aircraft carrier does not suggest China is on an aggressive military buildup. It says that China was the only UN Security Council member that did not have an aircraft carrier. Regional rivals India and Thailand have aircraft carriers.

The significance of the carrier is more in its symbolism than its strategic place in current power balance dictated by nuclear arsenal and unconventional firepower.

"Its symbolic significance outweighs its practical significance," Ni Lexiong, an expert on Chinese maritime policy at the Shanghai University of Political Science and Law, told Reuters.

"We're already a maritime power, and so we need an appropriate force, whether that's aircraft carriers or battleships, just like the United States or the British Empire did," he said.

It will take China several more years before it can deploy the aircraft carrier as a military tool. But the perceived aggression in China's recent defense postures has rattled neighbors and rivals.