SEOUL, South Korea — Defying both China and Japan, South Korea announced on Sunday that it was expanding its air patrol zone for the first time in 62 years to include airspace over the East China Sea that is also claimed by Beijing and Tokyo.

South Korea’s expanded “air defense identification zone” was the latest sign of a broadening discord among the Northeast Asian neighbors, who are already locked in territorial and historical disputes.

With South Korea’s newly expanded zone, the air defense zones of all three countries now overlap over a submerged reef called Ieodo in South Korea and Suyan Rock in China. The reef is controlled by South Korea, which maintains a maritime research station there, but China also claims it. The seabed around the reef is believed to be rich in natural gas and minerals deposits.

The South Korean move came two weeks after China stoked regional tensions by unilaterally expanding its own air patrol zone to partly overlap with South Korea’s and include airspace over the reef. The expanded Chinese air control zone also covers a set of East China Sea islands, called Diaoyu in Chinese and Senkaku in Japanese, which are at the heart of a territorial feud between Japan and China.