TAIPEI (Reuters) -Taiwan’s defence ministry said on Friday that a Chinese weather balloon had crossed the Taiwan Strait median line on Thursday, about a month before Taiwan’s presidential election.

“Our initial understanding is that it was a sounding balloon,” Taiwan Defence Minister Chiu Kuo-cheng told reporters at parliament.

Taiwan, which China claims as its own territory, frequently accuses Beijing of seeking to exert military or economic pressure to sway its elections toward outcomes favourable to the Chinese government.

The island will hold presidential and parliamentary elections on Jan. 13.

China has stepped up its military pressure against Taiwan over the past four years, including staging two rounds of major war games around the island in the past year and a half. On Tuesday, Taiwan reported rare nighttime Chinese military activity around the island, including aircraft crossing the sensitive median line.

The defence ministry said the balloon was detected 101 nautical miles (187 km) southwest of the northern Taiwanese city of Keelung, and travelled eastward for about an hour before disappearing.

Earlier this year, the defence ministry said a balloon that came down on a remote Taiwanese-held islet close to China’s coast was used for weather monitoring and had no audio-visual recording equipment on board.