China ships enter waters near disputed islands
14 September 2012 Last updated at 09:48 BST
Six Chinese surveillance ships have entered waters near islands claimed by both Japan and China.
China said the ships were carrying out "law enforcement" to demonstrate its jurisdiction over the islands, known as Diaoyu in China and Senkaku in Japan. The move came after Japan sealed a deal to buy three of the islands from their private Japanese owner.
Japan controls the uninhabited but resource-rich East China Sea islands, which are also claimed by Taiwan.
The BBC's Rupert Wingfield-Hayes explains the political background to the tension.