Japan's prime minister has urged China to act as a responsible member of the international community and raised concern over its expanding maritime activity in Asia, including in disputed waters where a ship collision ignited a bitter diplomatic feud. He called on both countries to deepen relations and promote economic cooperation to contribute to regional peace. Prime Minister Naoto Kan's comments came after three Japanese held by China for allegedly entering a restricted military zone returned home a sign that tension between the two Asian giants was easing somewhat.Still, Kan took a serious tone in his first major policy speech to parliament since surviving a leadership challenge last month, stressing the need for Japan to adopt a more active diplomacy and defence policy that can deal with uncertainty and instability that exist in areas surrounding our country.In response, China called for Japan to keep up the relationship.