Tokyo: The number of Chinese maritime incursions near Japanese-held islands in the East China Sea soared to a record this year, illustrating simmering tensions between Asia's two biggest economies.

Chinese government ships, including coast guard vessels, have entered what Japan considers its exclusive waters more than 1000 times this year, according to data from the Japan Coast Guard. That's on track for an 80 per cent increase over last year, and far more than any year since 2012, when China began making regular incursions around the islands.

The patrols - along with the recent detention and release of a Japanese academic accused by China of stealing state secrets - show how key disputes between the two neighbors remain unresolved even as they publicly tout warming ties.

Japanese Prime Minister Shinzo Abe is expected make his second trip to China in little more than a year later this month, and is hoping to host Chinese President Xi Jinping on a state visit next year.