They were arrested at separate locations in the northern Basque Country in an operation by police and customs investigators to stop an “imminent” shipment to Russia, an interior ministry statement said.

“The raid was launched to prevent the imminent dispatching from the EU territory of equipment for the cockpits of military aircraft,” it said, without saying when it happened.

Investigators were tipped off in June 2021 about a married couple, both Ukrainians, who were running a Spanish company “evading existing export controls, thereby committing a smuggling offence”.

While checking the firm’s export records, investigators discovered a network to supply military equipment to Moscow’s aeronautical sector with a “profound knowledge of transportation logistics”.

It had designed a “sophisticated system of international customs documentation” that allowed it to ship goods “to countries not facing an embargo when in reality the destination was Russia”.

Investigators arrested two suspects – a Ukrainian and a Russian – one of whom was running the network, the statement said.

A police spokeswoman was not able to clarify whether the detained Ukranian was one of the two people running the company. One of the suspects has been placed in pre-trial detention.

During the raid, investigators also seized documentation and computer equipment as well as two high-end vehicles.

The statement said Russia’s military industry had been “severely impacted” by an EU arms embargo.

The EU first banned arms exports to Moscow following Russia’s annexation of Crimea in 2014, but has significantly tightened the rules through sweeping sanctions imposed over its invasion of Ukraine in February 2022.