TAIPEI (Taiwan News) — Several Chinese fighter jets flew over Taiwan's airspace on Tuesday (June 9) following reports of a U.S. Navy transport jet seen flying directly over Taiwan.

The Ministry of National Defense said several Sukhoi-30 (Su-30) fighter jets briefly flew over the southwestern part of the nation's Air Defense Identification Zone (ADIZ), and Taiwan's Air Force quickly responded by broadcasting an order to drive them away.

The ministry said it has closely monitored the nation's surrounding ADIZ and has taken proactive measures to ensure the island nation's security.

It was the ninth time this year that Chinese military aircraft have been seen close to Taiwan's ADIZ. The presence of Chinese military aircraft this year was recorded on Jan. 23, Feb. 9, Feb. 10, Feb. 28, March 16, April 10, May 8, and May 16.

The planes crossed the median line of the Taiwan Strait and into the island nation's ADIZ on Feb. 10. The Chinese maneuvers were usually soon followed by sightings of U.S. military jets around Taiwan's ADIZ.