Tokyo, Japan - Japan scrambled military jets after Chinese planes allegedly violated the country's sovereign airspace on Monday morning.

A Chinese Y-9 intelligence aircraft briefly entered Japanese airspace at 11:29AM on Monday morning, a little ways off the coast of the Ganjo Islands in Japan's south-west Nagasaki prefecture.

This would be the first time that a Chinese military aircraft has incurred into Japan's airspace since World War 2, and comes at a time when tensions in the South and East China Sea are at a high.

In a statement provided to Japan's public broadcaster NHK, a Japanese defense ministry spokesperson said that the violation lasted two minutes.

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The plane then proceeded to circle the islands for a little under two hours, before flying back towards China.

"This violation of Japanese airspace is extremely regrettable," the spokesperson told NHK. "We have lodged a very strong protest through diplomatic channels to the Chinese government and strongly urged them to prevent a recurrence."

Japan and China are at loggerheads over a string of islands in the East China Sea, south of mainland Japan and north of Taiwan, known as the Senkaku Islands by Japan and Diaoyus by Beijing.

While Japan administers the islands, China has repeatedly claimed that they are its sovereign territory. Tokyo's position is that the islands are "clearly an inherent part of the territory of Japan."

The incident came amid growing tension between China and the US, as well as escalating confrontations with the Philippines over disputed territory.