China’s exports of rare earth permanent magnets to Japan slightly rebounded in April after slumping the previous month, but Japanese firms warn they are facing “severe” shortages as a diplomatic row between Beijing and Tokyo grinds on.

Shipments of permanent magnets from China to Japan rose by 2.5 per cent in April compared with the previous month, according to Chinese customs data released on Wednesday. But the modest rise only partly offset the 17.3 per cent plunge recorded in March.

The slowdown has raised alarm among Japan’s industrial giants, as permanent magnets are essential components for a range of hi-tech products – from electric cars to advanced weaponry. China is the world’s largest supplier of the magnets.

Japan ranked just ninth among buyers of Chinese permanent magnets last month, with Germany, South Korea and the United States making up the top three.

The data comes as Beijing and Tokyo continue a diplomatic feud that first erupted in November, when Japanese Prime Minister Sanae Takaichi suggested that a hypothetical attack on Taiwan could constitute an “existential threat” to Japan.

The remarks raised tensions with Beijing, which took a series of actions to restrict China’s economic ties with Japan – including warning its citizens against travelling to the country.

In January, China banned exports of “dual-use” items – or goods with potential military applications – to Japan. While the ban did not specifically name them, rare earth elements are sometimes classed as dual-use items, as are products such as drones and advanced semiconductors.