Beijing has hit back at accusations that a China state-sponsored actor was behind a cyber breach at the US treasury department, calling the claims “groundless”.

The breach was orchestrated via a third-party cybersecurity service provider. Hackers were able to gain access to a key used by the vendor to override certain parts of the system, according to a letter the treasury department sent to lawmakers on Monday.

According to the treasury, the incident happened earlier this month, when the actor was able to remotely access workstations and some unclassified documents.

On Tuesday, China denied the claims, with the foreign ministry saying Beijing “has always opposed all forms of hacker attacks, and we are even more opposed to the spread of false information against China for political purposes”.