Chinese ships sailed through disputed waters off Tokyo-controlled islands on Monday, days after Japan's Prime Minister Shinzo Abe caused an international stir by comparing Sino-Japanese relations with the run-up to World War One.
Three Chinese coastguard vessels spent around two hours in the 12-nautical-mile territorial waters off one of the Senkakus, which China claims and calls the Diaoyus, Japan's coastguard said.
It came as Abe was in New Delhi, where he and Indian counterpart Manmohan Singh affirmed plans to strengthen defence cooperation, including conducting joint maritime exercises on a "regular basis with increased frequency".
His three-day visit to India is being keenly watched by China, analysts say. Beijing is sometimes uneasy about what it sees as an attempt by the US-backed Japan to encircle it.
Beijing also has an often-fractious relationship with Delhi, partly because of a border dispute that erupted into a brief war in 1962. India is keen to burnish friendships in the region to offset its neighbour's growing might.
Abe was in Delhi days after he drew a comparison between Japan and China's relations and those of Britain and Germany as they stumbled towards World War One.
For its part, Beijing has sought to conjure the spectre of Nazism by comparing Abe with Hitler and urging him to emulate Germany's post-war contrition.
Chinese state-owned ships and aircraft have approached the Senkakus on and off to demonstrate Beijing's territorial claims, especially after Japan nationalised some of the islands in September 2012.