Story highlights 820-foot-long flattop designed to carry 14 helicopters

Launch comes at a time of increased tensions with China

China warns Japan against military expansion

Launch comes on 68th anniversary of Hiroshima bombing

Japan on Tuesday unveiled its largest warship since World War II, an 820-foot-long, 19,500-ton flattop capable of carrying 14 helicopters, according to media reports.

The ship, named the Izumo, is classified as a helicopter destroyer, though its flattop design makes it look like an aircraft carrier.

But the Japanese Defense Ministry says the ship is not intended to be used as an aircraft carrier and will not be used to launch fighter jets, state broadcaster NHK reported

The launch of the $1.2 billion warship at a Yokohama dockyard comes at a time of increased military tensions between Japan and China over disputed islands in the East China Sea.

"The destroyer is aimed at better responding to various contingencies in waters near Japan," NHK reported.

China on Tuesday warned Japan against any moves of military expansion, according to a report from Global Times

"We are concerned over Japan's constant expansion of its military equipment. Japan's Asian neighbors and the international community need to be highly vigilant about this trend," the Global Times quoted the Chinese Defense Ministry as saying. "Japan should learn from history, adhere to its policy of self-defense and abide by its promise to take the road of peaceful development."

Both China and Japan claim sovereignty over the rocky, uninhabited islands between Okinawa and Taiwan, which are near important shipping lanes, rich fishing grounds and possible mineral deposits. They are known as Senkaku in Japanese and Diaoyu in Chinese.

Last year, the Japanese government bought several of the islands from a private owner, angering Chinese authorities and provoking a spate of sometimes violent anti-Japanese demonstrations in many Chinese cities.

JUST WATCHED Disputed islands buzzing with activity Replay More Videos ... MUST WATCH Disputed islands buzzing with activity 02:18

Chinese government ships have continued to frequently sail near the islands, engaging in maritime games of cat and mouse with Japanese coast guard vessels. Chinese planes have also flown through the area, prompting Japan to scramble fighter jets.

Tuesday's launch also came on the 68th anniversary of the atomic bomb attack on Hiroshima.

Upwards of 60,000 people -- according to various estimates, about one-fifth of Hiroshima's population at the time -- were killed when a U.S. B-29 bomber dropped the bomb on August 6, 1945,