Chinese customs officers in eastern Shandong province have seized 60,000 maps that 'mislabelled' the self-governed island of Taiwan, which Beijing claims as part of its territory.

The maps, authorities said, also 'omitted important islands' in the South China Sea, where Beijing's claims overlap with those of its neighbours, including the Philippines and Vietnam.

The 'problematic' maps, meant for export, cannot be sold because they 'endanger national unity, sovereignty and territorial integrity' of China, authorities said.

Maps are a sensitive topic for China and its rivals for reefs, islands and outcrops in the South China Sea.

China Customs said that the maps also did not contain the nine-dash line, which demarcates Beijing's claim over nearly the entire South China Sea. The line comprises nine dashes which extends hundreds of miles south and east from its most southerly province of Hainan.

The seized maps also did not mark the maritime boundary between China and Japan, authorities said. Authorities clarified that the maps mislabelled 'Taiwan province', but did not specify what the error was.

China sees self-ruled Taiwan as its territory and has not ruled out the use of force to take the island. However, Taiwan considers itself distinct from the Chinese mainland, possessing its own constitution and democratically elected leaders.

Tensions in the South China Sea have recently escalated, most notably when ships from China and the Philippines encountered each other. Manila accused a Chinese vessel of deliberately ramming and using a water cannon against a Philippine government ship. Beijing countered that the Philippine vessel ignored multiple warnings and approached dangerously.

The Philippines and Vietnam are particularly sensitive to how the South China Sea is depicted in maps. For example, the Barbie movie from 2023 faced a ban in Vietnam and censorship in the Philippines for displaying a map with the nine-dash line.

China Customs did not disclose where the seized maps were intended to be sold. The confiscation of such maps is not unusual, though the scale of this seizure is notably larger than past incidents. Goods failing inspection at customs are typically destroyed.

In previous incidents, customs officers have seized maps that contain 'obvious errors' in national borders or misdrawings of international boundaries.