TAIPEI – At first the Taiwanese soldiers ignored the drones flying from China. Then, as the flights increased, they fired warning shots. Finally, the soldiers shot one into the sea.

In the past month, nearly 30 unarmed drones have buzzed two islands controlled by Taiwan near China’s southern coast. The drones were mostly civilian, or unidentified, but were clearly targeting the garrison of Taiwanese soldiers stationed on the rocky outcrops.

The drones are adding to tensions between the two sides that have escalated in the past month to new highs.

China – which regards Taiwan as a renegade province awaiting reunification with the mainland, by force if necessary – has intensified the presence of its military in the Taiwan Strait, flying jets and sailing ships ever closer to the island, testing its defences and raising the risk of conflict.

“China is using such harassment to increase pressure, deliberately raising tensions around Taiwan,” said Chieh Chung, an analyst at Taiwan’s National Policy Foundation. “Don’t assume that a civilian drone has nothing to do with military purposes.”

The question is how Taiwan will respond to future Chinese drone flights that might enter its airspace and whether it can deter Beijing without provoking conflict.

In the past week, in addition to the usual assortment of warplanes, China’s military sent four drones into airspace near Taiwan, the island’s Defence Ministry said. China flew the TB-001, a combat drone also known as the Twin-Tailed Scorpion, on Thursday, and two reconnaissance drones on Friday and Saturday, according to Taiwan.

For China, the military drones could be used to collect intelligence. The civilian drones are a new source of domestic propaganda aimed at undermining Taiwan’s image.

On Chinese social media, photographs taken by one drone showed two Taiwanese soldiers looking surprised and hapless. Some images showed the contrast between the soaring skyscrapers of the Chinese city of Xiamen and the scrappy conditions of the Taiwanese soldiers on the islands. Chinese commentators mocked soldiers for throwing rocks at the drones.

For Taiwan, the drones represent the latest front in China’s mounting campaign of intimidation and psychological warfare, known as “grey zone” tactics. The frequent incursions put pressure on Taiwan’s government to respond firmly.

President Tsai Ing-wen has warned China that Taiwan’s military will not stand by in the face of aggression.

“We will not provoke disputes, and we will exercise self-restraint, but it does not mean that we will not counter,” she said in a recent speech on the Penghu Islands in the Taiwan Strait.

On Sept 1, two days after Tsai’s speech, the Taiwanese soldiers downed the civilian drone, a move that was unusual for Taiwan, which has largely been restrained in pushing back against China.