The statement comes amid increased tensions between the two countries over the source of the outbreak.

The statement said the FBI was investigating digital break-ins by cyber-actors linked to China who were trying to steal data on vaccines, treatments and testing.

It warned scientists and public health officials to be on the lookout, but didn’t identify the institutions that had been targeted. The US authorities have long accused the Chinese government of cyber-espionage, which Beijing denies.

But this warning coincides with a much broader surge in cyber-theft and attacks by nations seeking advantage in the pandemic. Last week the US and Britain issued a joint statement about cyber threats to medical research, but didn’t name a specific country.