Taiwan's defense ministry said Friday it had detected a Chinese balloon crossing the so-called median line which bisects the sensitive strait that separates the island from China.

"1 PRC (People's Republic of China) balloon was detected at 11:52 (0352 GMT) yesterday after crossing the median line of the Taiwan Strait at the location (of) 101 nautical miles (187 kilometers) southwest of Keelung," said the ministry, referring to a city in northern Taiwan.

"The balloon headed east and disappeared at 12:55 (0455 GMT)," it added.

The ministry included a graphic showing the balloon on a meandering path.

The day before, the ministry reported it had detected seven Chinese aircraft crossing the median line at 7:30 p.m. 

"The aircraft also conducted joint combat patrol with (Chinese) vessels," it reported Thursday, adding that it had monitored and tasked "land-based missile systems to respond".

A Friday morning report said 27 planes had crossed the line in a 24-hour window ending at 6:00 a.m.

China has in recent years ramped up military and political pressures on democratic Taiwan, which it claims as its territory.

While Beijing has been sending warplanes and vessels around Taiwan on a near-daily basis, nighttime activity by Chinese aircraft and the appearance of a balloon are rare.