Japan's top government spokesman says the government is greatly alarmed by the entry of a Chinese naval vessel into areas just outside Japan's territorial waters near the Senkaku Islands. 
Chief Cabinet Secretary Yoshihide Suga told reporters on Thursday that the entry earlier in the day had unilaterally enhanced tensions. It's the first time a Chinese naval ship has sailed in the area, according to (NHK World). 
Suga said the latest move follows repeated intrusions by Chinese government ships into Japanese territorial waters off the islands. He said Japan is seriously concerned. 
Suga reiterated the Japanese government's stance that the Senkakus are an inherent part of Japan's territory historically as well as in international law. 
He vowed that the government will respond firmly and calmly, based on a determination to defend its territorial land, sea and airspace. 
He said the government will work closely with the United States and other members of the international community and urge China not to raise tensions.
Suga added that Japan has also warned Russia through diplomatic channels over navigation by 3 Russian warships in a contiguous zone outside the territorial waters off the Senkakus from Wednesday night to early Thursday morning. 
Vice-Minister for Foreign Affairs Akitaka Saiki has summoned China's Ambassador to Japan to protest the incursion of a Chinese navy vessel in the contiguous zone just outside Japanese territorial waters near the Senkaku Islands in the East China Sea. 
Saiki said he strongly condemns the entry of the navy vessel into Japan's contiguous zone. 
He also demanded that the vessel swiftly move away from the zone.

Source : QNA