Japan says President Shinzo Abe pushed for improved relations with China during a brief meeting in Russia with Chinese President Xi Jinping.
Tokyo officials said Friday the five-minute exchange occurred on the sidelines of the G20 summit in Saint Petersburg.
Such a meeting had been in question, since Japan-China ties have been damaged by a flare-up over a decades-old territorial dispute.
China's official Xinhua news agency acknowledged the two leaders met Thursday after Mr. Xi "encountered" Mr. Abe in a VIP room at the G20 summit.
Xinhua said Mr. Xi expressed concern that China-Japan ties face "grave difficulties" that Beijing is "unwilling to see."
But on Thursday, a Chinese delegation spokesperson at the summit said the responsibility for improved relations "does not lie with China."
China was angered after Japan last year purchased a group of disputed islands in the East China Sea from their private Japanese landowner.
Beijing has since sent increased ships and airplanes to patrol the area, raising fears of a military clash. The islands, known as Senkaku in Japan and Diaoyu in China, are surrounded by rich fishing grounds and possible energy reserves.
President Abe, who came to power in December, has taken a firm stance on the island dispute. But he has also pushed for high-level dialogue with China to help improve ties. Beijing has so far refused to hold such talks.
A Friday editorial in Xinhua, which often reflects official opinions, said China's refusal to hold bilateral talks is a "strong message that Tokyo is responsible" for the deterioration in ties. It called Mr. Abe's call for dialogue insincere.
Relations between the world's second and third largest economies have also been complicated by recent statements of some Japanese officials that Beijing have interpreted as a denial of Tokyo's wartime past.