TOKYO, Japan - The Japanese Maritime Self-Defense Forces' have put into service the largest Japanese warship since WWII, making additional manpower and carrying capacity available for island defense and disaster relief.

The 248m Izumo, dubbed "a helicopter carrier destroyer," is 25% longer than Japan's Hyuga-class destroyers and has a larger crew by 90 people, taking its total compliment to 470.

With its long continuous flight deck, Izumo can carry nine helicopters, five more than her smaller fleetmates. The ship can also hold about 50 3.5-ton trucks, which will help it carry out joint operations with the Ground SDF.

The ship was built at a cost of around 120 billion yen (US $1-billion), and is based at Yokosuka.

It will play a coordinating role among other vessels and aircraft, flexing its advanced command and communications capabilities and will eventually carry Osprey vertical takeoff and landing aircraft.

Izumo and its yet unnamed sister ship (DDH 184) are replacing JS Shirane (DDH 143) and JS Kurama (DDH 144), put into service in 1980 and 1981, respectively.

DDH 184 is due to be launched in August by Yokohama-based shipbuilder IHI Marine United and will be officially commissioned in March 2017.

According to IHS Jane's Fighting Ships, Izumo is equipped with an OQQ-22 bow-mounted sonar for submarine detection while air defence is provided by two Raytheon RIM-116 Rolling Airframe Missile SeaRAM launchers and two Phalanx close-in weapon systems.

The ship is optimised for anti-submarine warfare and can embark Sikorsky/Mitsubishi SH-60K Seahawk anti-submarine helicopters. The Izumo class's air wing will also include two airborne mine countermeasures versions of the Kawasaki Heavy Industries/AgustaWestland MCH-101 helicopter.

Japanese naval officials say that the ship will be deployed mainly for border surveillance and humanitarian assistance and disaster relief missions, but security analysts say the new class of carriers is also a direct response to China's claims on Japanese territories in the East China Sea.

Officials in Tokyo have confirmed the ship could play a command-and-control role in any operations to protect Japanese territories in the East China Sea, but have insisted there are no plans to use the vessel as an aircraft carrier.