TOKYO — More than 3,000 Japanese staged an anti-China demonstration in Tokyo Saturday amid a diplomatic row between the two Asian powers.The protesters, led by conservative groups, demanded China give up its claim to a group of disputed islands in the East China Sea. Police said the demonstration was peaceful.Waving Japanese flags, the demonstrators held banners reading "Condemn China's militaristic hegemony over Asia" and "Senkaku islands are Japanese territories."China and Japan have locked horns over the sovereignty of small islands called Diaoyu in China and Senkaku in Japan. The islands are controlled by Tokyo but also claimed by Beijing.The long-running dispute over the islands flared after a September collision between Japanese patrol vessels and a Chinese fishing boat. The Chinese boat captain was arrested but later released.The standoff sparked anti-Japan rallies in several Chinese cities.Saturday's anti-China protest in the Japanese capital came a day after Japan launched a probe into the possible leak of a video showing the collision. The video first appeared on YouTube on Friday, and was widely picked up by Japanese television networks.Japanese media reported that several government sources had confirmed the authenticity of the video. But coast guard spokesman Daisuke Hirasawa declined to confirm the reports Saturday."We are in the middle of investigation. We cannot give any information at this point," he said.The video showed a ship bumping a Japanese vessel, while sirens wailed in the background and the Japanese crew shouted orders for the ship to stop.It raised concerns of rekindled tensions ahead of an international summit in Japan next week. Tokyo hopes to have a meeting with China's leader on the sidelines of the summit.After the September collision, China demanded an apology and compensation, but Tokyo countered by demanding that Beijing pay for damage to the patrol boats.China cut off ministerial-level contacts with Japan, repeatedly called in Tokyo's ambassador to complain, and postponed talks on the joint development of undersea natural gas fields.