Taiwan's defense ministry says eight Chinese military planes crossed the Taiwan Strait's median line and came close to Taiwan's contiguous zone.

The ministry said 19 Chinese military aircraft were detected around Taiwan's airspace on Saturday morning. It said eight of them flew close to Taiwan's contiguous zone that is 24 nautical miles, or about 44 kilometers, off its coast.

Officials didn't disclose the types of the eight aircraft or their flight paths.

The ministry also said it detected five Chinese military vessels at about the same time.

It said authorities were aware of all Chinese military activities and closely monitored them with aircraft, vessels and land-based systems.

Taiwan defines its territorial sea as a belt of waters extending 12 nautical miles from its coastline. It also defines its contiguous zone as an area of waters extending 12 nautical miles beyond the territorial sea.

Chinese military jets have frequently crossed the median line since last August, when then US House Speaker Nancy Pelosi visited Taiwan.

Taiwan is on high alert. If China flies military aircraft over the contiguous zone, it would inflame tensions.