TAIPEI: Taiwan's defence ministry said it had detected three more Chinese balloons flying across the Taiwan Strait on Wednesday, and one of those flew over the island, the second day in a row it has reported such activity.

The potential for China to use balloons for spying became a global issue in February 2023 when the United States shot down what it said was a Chinese surveillance balloon. China said the balloon was a civilian craft that accidentally drifted astray.

Taiwan is on high alert for Chinese activities, both military and political, ahead of Jan. 13 presidential and parliamentary elections. It says China is exerting military and economic pressure in an attempt to interfere in the elections.

China views the island as its own territory, a claim Taiwan's government rejects.

Taiwan's defence ministry has since last month reported several instances of Chinese balloons flying over the sensitive Taiwan Strait, then crossing airspace to the island's north before vanishing.

But this week alone it has reported two back-to-back incidents of balloons actually crossing the island.

On Thursday in its daily update of Chinese military activity over the previous 24 hours, the ministry said three Chinese balloons had again flown over the strait, one of which crossed over the centre of Taiwan island before vanishing.

The northerly balloon was spotted 45 nautical miles (83 km) north of Hsinchu, a city home to a Taiwanese air force base, while the other two flew just north of the Penghu islands, where there is another air base.

However a map provided by the ministry showed only one balloon flying over Taiwan island.

The ministry, which has previously said it believed they were mostly for weather monitoring, said it would not comment on what the latest balloons may have been used for.

China's defence ministry did not immediately respond to a request for comment. Last week it declined to comment on the balloons.

Over the past four years China has stepped up military activity around Taiwan and Chinese fighter jets and warships now regularly operate in the strait.