The People's Liberation Army (PLA) exercise took place Wednesday and involved various types of helicopters that tested "all-weather operational capability of the air force at sea," the official Xinhua news agency said.

State broadcaster CCTV showed footage of helicopters firing missiles at distant objects in the water.

The reports did not say exactly where the exercises took place, but they occurred on the same day that China conducted live-fire drills in the Taiwan Strait.

Beijing had announced the Taiwan Strait drills last week, further ramping up tensions following stark warnings against any independence moves by the self-ruled island, which China sees as its sovereign territory.

Vessels had been ordered to avoid a certain area off the Chinese mainland's coast, triggering speculation that a flotilla spearheaded by China's sole aircraft carrier would take part in the exercise.

But Taiwan's defence ministry said Wednesday that the drills only involved land-based artillery conducting "routine" shooting practice, accusing Beijing of exaggerating its plans as a form of "verbal intimidation and sabre-rattling".

The drills coincided with Taiwanese President Tsai Ing-wen's visit to Swaziland, one of Taipei's few remaining international allies.

Beijing has stepped up military patrols around Taiwan and used diplomatic pressure to isolate it internationally since Tsai took office.

China sees the democratically-governed island as a renegade part of its territory to be brought back into the fold and has not ruled out reunification by force.

Beijing has also been angered by Washington's arms sales to Taipei, and China protested last month after President Donald Trump signed a bill allowing top-level US officials to travel to Taiwan.

Washington switched diplomatic recognition from Taiwan to China in 1979 but maintains trade relations with the island.