BEIJING — In a ceremony attended by the country’s top leaders, China put its first aircraft carrier into service on Tuesday, a move intended to signal its growing military might as tensions escalate between Beijing and its neighbors over islands in nearby seas.

Officials said the carrier, a discarded vessel bought from Ukraine in 1998 and refurbished by China, would protect national sovereignty, an issue that has become a touchstone of the government’s dispute with Japan over ownership of islands in the East China Sea.

But despite the triumphant tone of the launching, which was watched by President Hu Jintao and Prime Minister Wen Jiabao, and despite rousing assessments by Chinese military experts about the importance of the carrier, the vessel will be used only for training and testing for the foreseeable future.

The mark “16” on the carrier’s side indicates that it is limited to training, Chinese and other military experts said. China does not have planes capable of landing on the carrier and so far training for such landings has been carried out on land, they said.