China flexed some maritime muscle Friday in its dispute with Japan over a chain of uninhabited islands, holding naval exercises in the East China Sea to demonstrate its ability to enforce offshore territorial claims.

Both countries have been displaying their naval prowess during an unexpectedly bitter dispute over the islands, called Diaoyu in Chinese and Senkaku in Japanese. Tokyo angered Beijing last month by nationalizing some of the islands, in a move that sparked violent protests in China.

Nearby Taiwan also claims the islands, which are uninhabited but surrounded by rich fishing grounds and possibly lucrative undersea energy deposits.

Friday's exercise involved 11 vessels from the East China Sea fleet and the civilian marine surveillance and fishery administration agencies, the official Xinhua News Agency said. Eight aircraft also took part, it said.

The drills focused on patrol tactics and responses to emergencies that threaten China's territory, Xinhua said. State TV footage showed a frigate, a fighter jet and some helicopters participating. While the exact location of the exercises wasn't known, TV showed the vessels and aircraft operating near shore, not on the high seas or close to the disputed islands.

State media accounts of the exercises linked them to recent disputes.

Xinhua said patrol vessels from the fishery administration and the marine surveillance agency have recently been stalked and harassed by foreign vessels while carrying out missions.

"The struggle to protect sovereignty faces many challenges," it said.

On Tuesday, Japanese military aircraft spotted seven Chinese warships not far from the disputed islands. China said the ships were on a routine training mission, although they passed between a pair of islands in Japan's southern Yaeyama chain in what Japanese officials said was a first for the Chinese navy.

On Sunday, Japan's navy marked its 60th anniversary with a major exercise involving about 40 ships — including state-of-the-art destroyers, hovercraft able to launch assaults on rough coastlines and new conventionally powered submarines. For the first time, Japan's navy was joined by warships from the United States, Singapore and Australia. Representatives from more than 20 countries, including China, attended the event staged in waters south of Tokyo.

Japan also plans to hold a joint exercise with the U.S. military later this year, reportedly using a scenario of taking a remote island back from a foreign intruder.

China's exercise also takes place after dozens of Japanese parliament members, including two Cabinet ministers, visited the Yasukuni Shrine in Tokyo, which honors 2.5 million war dead but also commemorates 14 Japanese wartime leaders convicted of war crimes. Chinese media slammed the head of Japan's top opposition party for also going, calling his visit a provocation.