The Japanese government summoned China's ambassador on Tuesday to protest four Chinese maritime surveillance ships that spent about 13 hours in waters near disputed islands claimed by both countries, according to a report of the Associated Press. Deputy Foreign Minister Akitaka Saiki summoned Ambassador Cheng Yonghua to the Ministry of Foreign Affairs after the four Chinese government ships entered waters off the islands for about 13 hours Monday until early Tuesday, ministry official Masaru Sato said. Asked about the reprimand during a routine briefing, Chinese Foreign Ministry spokesman Hong Lei reiterated Beijing's stance that the islands are "an inherent part of Chinese territory," and said the Chinese vessels were carrying out normal official duties. "We do not accept Japan's protests and representations," Hong said.