KUALA LUMPUR: Malaysia’s air force scrambled jets to intercept 16 Chinese military aircraft off the country’s coast in the South China Sea, a rare incident officials said Tuesday threatened “national sovereignty”.

The incident took place Monday off the Malaysian part of Borneo island over the fiercely contested waters, where China and Malaysia have overlapping territorial claims.

The Chinese air force transport planes approached Malaysian airspace in “tactical formation” and flew to within about 60 nautical miles of the coast, Malaysia’s air force said in a statement.

They were spotted by radar and several attempts were made to contact the planes. As they approached, the air force sent planes to intercept and identify them, and they did not enter the country’s airspace before flying off. The Malaysian air force described the appearance of the planes as “suspicious”.

“This incident is a serious matter in regards to national sovereignty and aviation safety,” as the area is a busy place for aircraft, the statement said. The foreign ministry did not respond to requests for comment. China has laid claim to nearly all of the South China Sea and has built numerous military outposts on small islands and atolls, angering other countries with competing claims to the waters.