Earlier in the day, Japan's Kyodo news agency said that Tokyo expressed concern over the crossing of a Chinese navy ship in a contiguous zone just outside Japanese territorial waters near the disputed Senkaku Islands in the East China Sea, which are claimed by both Tokyo and Beijing.
"The unilateral actions that result in increasing tensions are causing concern. We would like to avoid the escalation of the situation, but in the event of invasion into territorial waters, we will react correspondingly," Kawano said.
Relations between Japan and China have been strained by a dispute over uninhabited islands in the East China Sea. The Japanese, who have claimed the islands since the 19th century, call them the Senkaku Islands, the name mostly recognized globally, while in China they are known as the Diaoyu Islands.
In 2014, Japan and China agreed to reduce tensions over the disputed islands. However, Chinese vessels repeatedly intruded into Japanese territorial waters around the Senkaku Islands in 2015.