Tensions between the two East Asian powers have been rising after Japanese Prime Minister Sanae Takaichi responded to a question in parliament last month by saying that any "contingency" involving Taiwan would also inevitably threaten the national security of Japan.
Beijing claims the island is part of China and insists it will be "reunited" with the mainland, by force if necessary. The pressure on Taiwan has increased in recent years and there are growing fears that China will attempt to seize the island.
Analysts say that successive Japanese governments have long held the same position on the Taiwan situation, but not previously stated it. The more forthright Takaichi, however, has been more explicit and is incurring Beijing's wrath.