BEIJING - China has obtained "adequate" evidence of Japanese warships and airplanes conducting close-range monitoring and surveillance of the Chinese navy, China's military spokesman said on Thursday.

"China will retain the right of adopting relevant measures," said Geng Yansheng, spokesman with the Ministry of National Defense, at a briefing.

Japanese warships and airplanes have for a long time closely followed, monitored and disturbed Chinese naval ships and airplanes, a practice which harms the security of the Chinese navy and aggravates current Sino-Japanese marine security problems, according to Geng.

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