The potential for China to use balloons for spying became a global issue in February when the United States shot down what it said was a Chinese surveillance balloon, but which China said was a civilian craft that accidentally drifted astray.
Taiwan is on high alert for Chinese activities, both military and political, ahead of the Jan. 13 presidential and parliamentary election. Taipei has warned of Beijing's efforts to interfere in the ballot to get voters to pick candidates China may prefer.
Taiwan's defence ministry said the two balloons were detected at 9:03 a.m. (0103GMT) and 2:43 p.m. (0643) after crossing the strait's median 110 nautical miles (204 km)northwest of the northern Taiwanese port city of Keelung.
The balloons flew at an altitude of about 27,000 feet (3,230 metres), headed east and disappeared at 9:36 a.m. and 4:35 p.m., respectively, the ministry added.
The ministry's initial judgement is that they were weather balloons, spokesperson Sun Li-fang said.
The earlier balloon, which Taiwan reported crossing the Taiwan Strait on Dec. 7, was most likely also a weather platform, Taiwan's defence ministry said at the time, adding that officials had announced its detection in the interests of transparency.
(Reporting by Ben Blanchard; Editing by Jacqueline Wong and Gerry Doyle)
