BEIJING, Aug. 1 (Xinhua) -- The Chinese People's Liberation Army (PLA) Southern Theater Command (STC) conducted a joint naval-air training exercise focusing on multiple realistic training subjects in the territorial sea and airspace of China's Huangyan Dao and its surrounding areas on Saturday.

The theater command said in a statement that relevant subjects included reconnaissance and early warning, deterrence patrol, air-sea control, and joint strike.

The exercise effectively honed the troops' naval-air coordination, rapid support and win-by-system capabilities, the statement said.

Huangyan Dao is an inherent part of China's territory, and the Philippines' delimitation of the so-called "baselines of the territorial sea" of Huangyan Dao is illegal and null, said the statement.

Forces of the STC will stay on high alert at all times and resolutely safeguard China's territorial sovereignty and maritime rights and interests, it added. ■