Japan's Coast Guard on Saturday said that the Chinese ships were cruising near the disputed islands in the East China Sea and repeatedly sent messages warning them not to enter the islets' territorial waters. The ships had responded to the radio messages by saying they were on a "justifiable mission". The Yuzheng 310 and the Yuzheng 201, both fisheries patrol vessels, left the area heading west in the mid-afternoon, the coastguard said in a statement.

Both Tokyo and Beijing claim the potentially resource-rich islets, known as the Diaoyus in China and Senkakus in Japan, along with the surrounding waters. A tense territorial raw broke out in September after Japan arrested a Chinese trawler captain in the area, bringing ties between the Asian rivals to their lowest point in years.

The arrest sparked serious protests from China, which cut or dramatically reduced political, cultural and economic exchanges with Japan. The two have since worked to get their relationship back on an even keel.

Japan's Nikkei newspaper reported Sunday that Tokyo plans to deploy around 100 ground troops to an island near the disputed islets by 2015, in response to Beijing's growing assertiveness in the area. The troops on Yonaguni, which lies around 150 kilometres (100 miles) southwest of the Senkakus will monitor warships and planes, the Nikkei said. The deployment is expected to trigger angry reactions from Beijing and Taipei, which also lay claim to the potentially resource-rich rocky islets and surrounding waters.