TAIPEI (REUTERS) – Suspected drones flew over outlying Taiwanese islands and hackers attacked its defence ministry website, authorities in Taipei said on Thursday, a day (Aug 4) after a visit by US House of Representatives Speaker Nancy Pelosi that outraged China.

Taiwan has been on alert as China conducts a series of military exercises in response to a visit to the island this week by Pelosi.

Some of the drills were to take place within the island’s 12-nautical-mile sea and air territory, according to the defence ministry in Taipei.

That has never happened before and a senior ministry official described the potential move as “amounting to a sea and air blockade of Taiwan”.

Taiwan’s ruling party said on Thursday that the Chinese military drills have triggered regional tensions and are illegitimate.

China is conducting drills on the busiest international waterways and aviation routes and that is irresponsible unilateral behaviour, the ruling Democratic Progressive Party said.

South-east Asian foreign ministers warned on Thursday that the growing standoff over Taiwan could spark “open conflicts”.

Ministers from the 10-member Asean issued a joint statement saying the situation “could destabilise the region and eventually could lead to miscalculation, serious confrontation, open conflicts and unpredictable consequences among major powers”.

China, which claims Taiwan as its own territory, said on Thursday its differences with the self-ruled island were an internal affair.

“Our punishment of pro-Taiwan independence diehards, external forces is reasonable, lawful,” the Beijing-based Taiwan Affairs Office said.

China’s Xinhua news agency has said the exercises, involving live fire drills, will take place in six areas which ring Taiwan and will begin at noon (0400 GMT).

On Wednesday night, just hours after Pelosi left for South Korea, unidentified aircraft, probably drones, had flown above the area of the Kinmen islands, Taiwan’s defence ministry said.

Major General Chang Zone-sung of the Army’s Kinmen Defence Command told Reuters that the Chinese drones came in a pair and flew into the Kinmen area twice on Wednesday night, at around 9pm and 10pm.

“We immediately fired flares to issue warnings and to drive them away. After that, they turned around. They came into our restricted area and that’s why we dispersed them,” he said.

The heavily fortified Kinmen islands are just off the southeastern coast of China, near the city of Xiamen.

“We have a standard operating procedure. We will react if they come in,” Mr Chang said, adding that the alert level there remained “normal”.

He said he believed the drones were intended to gather intelligence on Taiwan’s security deployment in its outlying islands.

Last week, Taiwan’s military fired flares to warn away a drone that “glanced” at its Matsu archipelago off the coast of China’s Fujian province and was possibly probing its defences, Taiwan’s defence ministry said.