Malaysia's foreign ministry says it will lodge a formal protest with China over an "intrusion" of 16 Chinese warplanes into its airspace earlier this week.
Malaysia's air force deployed fighter jets to intercept the planes after they were detected by radar about 60 nautical miles (about 111.12 kilometers) off the coast of Sarawak state on Borneo island, located in the South China Sea.
The planes were identified as Ilyushin iL-76 and Xian Y-20 strategic transporters flying at an altitude between 7 and 8 kilometers.
The foreign ministry called the incident "a serious threat to national sovereignty and flight safety."
"Malaysia's stand is clear - having friendly diplomatic relations with any countries does not mean that we will compromise our national security," Foreign Minister Hishammuddin Hussein later said in a statement.
The Chinese Embassy denied Kuala Lumpur's accusations, saying the planes were conducting routine flight training and strictly adhered to international law.
China has claimed territorial rights over nearly the entire South China Sea, ignoring overlapping claims by regional neighbors Brunei, Malaysia, the Philippines, Taiwan and Vietnam. It has aggressively expanded its military presence throughout the sea, building man-made islands and installing military outposts and aircraft landing strips.