China’s first aircraft carrier entered service Tuesday, the defence ministry in Beijing said, as the country expands its blue-water fleet at a time of increasing maritime tensions in the region.President Hu Jintao and Premier Wen Jiabao attended a "commissioning” ceremony for the 300-metre (990-foot) vessel, state media said.The former Soviet ship that was bought from Ukraine was renamed Liaoning after the northeastern province that is home to China’s main naval port city of Dalian, where it was refitted.The commissioning makes China the last permanent member of the United Nations Security Council to have an aircraft carrier, and comes as Beijing’s economic and political significance grows.Numerous sea trials of the aircraft carrier -- which was previously known by China only as "Number 16” -- since August 2011 were met with concern from regional powers including Japan and the United States, which called on Beijing to explain why it needed such a ship."The PLA’s general armament department, the navy and all comrades participating in the carrier program should make new contributions in promoting China’s weaponry construction and safeguarding national sovereignty, security and territorial integrity,” Wen said at the ceremony in Dalian."It will also be of great significance in enhancing national defence power and the country’s comprehensive strength.”The US previously played down the importance of the aircraft carrier, saying that it had "limited” capability following its first sea trial in August 2011.The Pentagon also said the vessel was the first step towards a future fleet of carriers expected to be built domestically in coming years.Taiwan’s intelligence chief said earlier this year that China has decided to build two aircraft carriers. However despite rumours that work has already begun, there is no evidence of construction of a domestically-built carrier.There had been speculation on what the vessel was to be called, with retired Major General Luo Yuan suggesting naming it Diaoyu, after islands in the East China Sea claimed by China, which are also claimed by Japan where they are known as Senkaku.Beijing on Sunday postponed a ceremony marking the 40th anniversary of the establishment of diplomatic ties with Tokyo.Tensions have also risen this year with Vietnam and the Philippines over disputed islands in the South China Sea.Beijing confirmed last year it was revamping the former Soviet ship -- originally called the Varyag -- and has repeatedly insisted the carrier poses no threat to its neighbours.It says the ship will mainly be used for training and development purposes, but military commentators say China is developing strike aircraft and support vessels which would help the ship become fully operational.AFP