This file aerial shot taken on September 15, 2010 shows the disputed islands known as Senkaku in Japan and Diaoyu in China in the East China Sea.
Japan's Foreign Ministry has summoned China's ambassador in protest at the sailing of Chinese ships near the group of islands in the East China Sea disputed by Beijing and Tokyo.
"The foreign ministry summoned the Chinese ambassador over ships entering the waters near Senkaku islands," said a anonymous Japanese foreign ministry official on Tuesday.
The protest move came the Japanese coastguard said on Monday that two maritime surveillance boats entered the waters of the islands and reportedly remained there for around 14 hours.
Japan and China have long been in a dispute over the sovereignty of the uninhabited islands, which are located near a crucial shipping lane and would give the owner exclusive oil, mineral, and fishing rights in the surrounding waters.
The islands, which are controlled by Japan and form part of Okinawa prefecture, are known as Senkaku in Japan and Diaoyu in China.
Japan's prime minister vowed on Saturday to defend the islands from threats by China.
"The security environment surrounding our country is increasingly becoming more severe as we face provocation to our territorial rights," Prime Minister Shinzo Abe said.
"I will take the lead to stand up against the present danger and protect the people's lives and asset, as well as our land, the seas and the air at all costs."
In recent weeks both states have dispatched fighter jets to the airspace of the disputed islands, although there have been no clashes.
Tensions heightened between the two countries after Japan signed a deal on September 11, 2012 to buy three of the islands from their private Japanese owner in line with plans to nationalize the archipelago.
Hundreds of Chinese held anti-Japan demonstrations following the announcement. Chinese ships have also since been sailing around the islands, eliciting angry reaction from Japan.