BEIJING  -- China is exercising "effective supervision" of its recently expanded air defense zone over the East China Sea in response to a South Korea-Japan joint naval drill in international waters covered by Chinese airspace, Beijing said Friday.

South Korea and Japan conducted the regular naval drill this week with two destroyers and two helicopters each from the two navies, South Korean military officials said. They practiced search and rescue operations, according to the officials.

As South Korea and Japan do not recognize the expanded Chinese air defense identification zone (ADIZ), announced by Beijing last month, their navies didn't inform the Chinese authorities of the use of helicopters there, they said.

Asked about the joint drill, China's foreign ministry spokesman Hong Lei told reporters, "We are already implementing effective supervision over the East China Sea ADIZ."

"Meanwhile, China is committed to upholding peace, order and stability in the region and in the relevant airspace," Hong said.

"We hope that relevant parties can work with China toward the same goal and make constructive efforts rather than the opposite."

Regional tensions have risen following China's Nov. 23 expansion of its ADIZ that overlaps those of South Korea and Japan.

It requires all aircraft entering the zone to notify Chinese authorities and follow their instructions or else face "defensive emergency measures."

The expansion of Chinese airspace, which includes a Seoul-controlled submerged rock, Ieodo, is mainly viewed as an attempt to bolster Beijing's claim over a set of islands at the center of a bitter territorial dispute with Japan.

South Korea on Sunday expanded its own air defense zone to cover Ieodo and other islands, prompting China to express regret over the move.(Yonhap News)