The live-fire drills that began Monday follow China's strident rejection of an international arbitration panel's ruling last month that invalidated Beijing's claims to a vast swath of the South China Sea.

That led to days of angry statements from Beijing, followed by live-firing naval exercises in the South China Sea and the launch of regular aerial patrols in the area.

On Tuesday, the Defence Ministry said the East China Sea exercises were aimed at improving the "intensity, precision, stability and speed" of its military.

"An information technology-based war at sea is sudden, cruel and short, which requires fast transition to combat status, quick preparation and high assault efficiency," the ministry said.

The drills include ships, submarines, aircraft and coast guard forces, illustrating China's growing emphasis on integrated training under realistic conditions.

China's navy has been closing the gap with its US rival in both ship numbers and technology, including the deployment of advanced anti-ship missiles, nuclear submarines and the country's first aircraft carrier.

While global attention has been drawn to the South China Sea, where five governments exercise territorial claims overlapping with China's, Beijing also operates extensively in the East China Sea, where it claims a string of uninhabited islands controlled by Japan.