Two Chinese ships were spotted near islands at the centre of a dispute between Beijing and Tokyo, Japan's coast guard said, as diplomats try to mend ties after a bitter row. A Japanese patrol aircraft saw an advanced Chinese fisheries patrol ship in waters near the island chain in the East China Sea around 8:25 am (2325 GMT) on Saturday, a coast guard spokeswoman said, before finding a second vessel 20 minutes later. Japanese patrol ships repeatedly told the vessels not to enter Japan's territorial waters, she said. The coast guard later said the Chinese ships were cruising around the disputed islands, responding to the radio messages by saying they were on a "justifiable mission". Both countries claim the potentially resource-rich islets, known as the Diaoyus in China and Senkakus in Japan, along with the nearby seas. The latest dispute broke out in September and has brought ties between the Asian rivals to their lowest point in years, fuelling nationalist anger in both nations. Leaders are now gradually trying to mend relations. Saturday's maritime encounter came after a helicopter-equipped advanced fisheries vessel left Guangzhou in China for the East China Sea on a mission that could last 20 days, according to a report Tuesday by the state Xinhua news agency. It was unclear whether a chopper was on board because the ship closed the shutter of its helicopter hangar, Japan's coast guard said. It was the first time since October 24 that Chinese patrol vessels had been seen operating in the region, Japan's Jiji Press reported. "The two vessels came as close as 23 kilometres (14 miles) to the islands," the coast guard spokeswoman said, adding that the ships had not entered what Japan considers its waters. "They seem to be travelling just outside our territorial waters," she said. The ship that set off from Guangzhou, the 2,580-ton Yuzheng 310, is "the fastest (of China's fishery patrol vessels) and had the most sophisticated technologies", Xinhua quoted an official as saying Tuesday. The other Chinese boat was identified as "Yuzheng 201", Japan's coast guard spokeswoman said. As of early afternoon, the Chinese ships continued to cruise in the area, travelling counterclockwise around the disputed islands, the coast guard said, while the Japanese ships continued to warn them not to enter Japan's waters. "To our warnings, Yuzheng 310 has repeated responses such as 'we are conducting a justifiable mission'," it said in a statement. The Japanese government has set up a team to relay up-to-date information on the situation to various ministries, Jiji Press said. The encounter comes as Japan and China attempt to get their relationship back on an even keel. The row erupted in September when the Japan Coast Guard arrested a Chinese trawler captain for allegedly ramming two of its vessels in the area. The arrest sparked serious protests from China, which cut or dramatically reduced political, cultural and economic exchanges with Japan. On the sidelines of a regional summit in Japan at the weekend, the two sides appeared to take a step beyond the dispute when Chinese President Hu Jintao held a meeting with Japanese Prime Minister Naoto Kan. Hu promised that China was committed to being a good neighbour, as concerns rise over its assertive behaviour in the Asia-Pacific.