Japan lodged a protest with China on Friday after three Chinese government ships entered Japanese territorial waters around a chain of disputed islands in the East China Sea. The Foreign Ministry conveyed the complaint in a phone call to the Chinese Embassy in Tokyo over the intrusion. The Japan Coast Guard said it spotted the three maritime surveillance ships that belong to China\'s State Oceanic Administration earlier in the day in sovereign waters off the Japan-administered Senkaku Islands, which are also claimed by China and Taiwan. The coast guard warned the Chinese ships to leave the area immediately, but the ships remained in the waters for about four hours. Violation of the Japanese territorials waters by Chinese vessels was the first since May 26. The small chain of uninhabited rocky islands, known as Diaoyu in China and Tiaoyutai in Taiwan, lie in rich fishing grounds and waters thought to contain large deposits of oil and natural gas. Relations between the world\'s second and third-largest economies have sharply deteriorated since Tokyo\'s nationalization of three of the five major islands in September last year through purchase from a private Japanese owner.