Japan has expressed its concern after a Chinese naval ship sailed near what it considers Japanese territorial waters in the East China Sea. This was the first time a Chinese naval ship has made its way into such waters.
Japan's Vice Foreign Minister Akitaka Saiki summoned the Chinese ambassador in Tokyo at around 2 a.m. (1700 GMT on Wednesday) to "express serious concern." He also reportedly urged the Chinese ship to leave the area.
The vessel - a 3,963-ton Jiangkai class frigate - was spotted by Japan's guided-missile destroyer Setogiri, the Japanese Defense Ministry said.
The UN Convention on the Law of the Sea states that a state's contiguous zone starts from the limits of its territorial waters, 12 nautical miles (22 kilometers) off shore, extending a further 12 nautical miles out to sea.
The Chinese Defense Ministry said the islands belong to China and that its ships have every right to sail through the island's waters, Reuters news agency reported.
Escalating regional tensions
Chief Cabinet Secretary Yoshihide Suga later criticized Beijing for escalating regional tension.
"The fact that [China] sent a naval ship to the contiguous waters of our Senkaku Islands for the first time is an act that unilaterally increases tension and our nation is gravely concerned," Suga told a regular briefing.
The Chinese ship entered waters shortly after midnight, the Foreign Ministry said. It left the waters about an hour later, sailing to the north, the Defense Ministry said.
"We will continue our calm handling of this issue so as not to unnecessarily escalate the situation," Japanese Defense Minister Gen Nakatani, currently visiting Thailand, told journalists.
Tokyo considers the territory in the vicinity of disputed islands, known as the Senkaku in Japan and the Diaoyu in China, to be its own territorial waters.
The uninhabited islands lie about 220 km (135 miles) northeast of Taiwan and are administered by Tokyo but claimed by Beijing. Chinese ships sailed near the disputed islands last year.
Relations between Japan and China deteriorated in 2012 when Tokyo "nationalized" some of the islets.
There have been some improvements in relations between the two countries, which had soured in recent years over their wartime history and territorial rows.
At around the same time, three Russian battleships entered waters close to what Japan considers its territory, the Defense Ministry said. None of the ships violated what Japan considers its territorial waters, it said.
jbh/sms (Reuters, AP, dpa, AFP)