Malaysia’s air force said it scrambled jets Monday to run visual confirmation following the airplanes flew over 60 nautical miles off Sarawak country of Malaysian Borneo.

It described the episode as a”serious danger to national sovereignty and airport security.”

The Chinese planes failed to get regional air traffic management despite being taught several days, the aviation.

Foreign Minister Hishammuddin Hussein said Malaysia will issue a note of diplomatic demonstration and inquire China’s ambassador to Malaysia to describe the”breach of their Malaysian airspace and sovereignty.”

“Malaysia’s stance is apparent — with favorable diplomatic relations with some states doesn’t indicate that we’re going to compromise on our domestic safety,” Hishammuddin said in a statement.

China’s embassy previously said that the airplanes conducted regular flight instruction and”strictly abided by” global law without breaking airspace of other nations.

China was pushing a grand claim within the South China Sea, by which approximately $3 trillion worth of ship-borne commerce passes annually. Additionally, it has constructed military centers on manmade islands.

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Brunei, Malaysia, the Philippines, Taiwan and Vietnam have claims to different islands and characteristics in the region and China’s coast guard regularly warns foreign ships and aircraft to depart what it requires its land.

Malaysia’s air force said the airplanes, including Ilyushin il-76 and Xian Y-20 tactical transporters, had traveled within an”in-trail” strategic formation in between 23,000 and 27,000 ft.