Hong Kong (CNN) -- China has expressed "regret" over South Korea's decision to expand its air defense zone to include an area claimed by both countries, the country's official Xinhua news agency has reported.
South Korea's move came after China declared an Air Defense Identification Zone (ADIZ) in the East China Sea last month. The Chinese zone covers a disputed reef, called the Suyan rock by China and Ieodo by South Korea.
China's foreign ministry spokesman Hong Lei said on Monday that the two countries had maintained communication over the zones.
"The Air Defense Identification Zone is not territorial airspace. It is established by a country in public airspace outside its territorial airspace for identification and early-warning. It has nothing to do with maritime and air jurisdiction," he said.
The expanded South Korean zone will go into effect on December 15.
South Korea Defense Ministry spokesman Kim Min-seok said the move was in accordance with international norms.
"The new KADIZ's southern region was adjusted so that it is in line with Incheon Flight Information Region, which is internationally used (recognized) and does not overlap with that of neighboring countries.
"The adjusted region includes airspace over Ieodo waters and Marado and Hongdo islands which is our territory."
China newly declared air defense zone has raised tensions in the region, with the United States, Japan and South Korea lodging objections to the zone.