President Vladimir Putin said on Wednesday that Russia will respond in kind if European countries start to seize Russian merchant vessels, and the commander of Russia’s Pacific Fleet said his forces were ready to “inspect and detain” foreign vessels from what he called hostile states.

The comments, which Putin made as he oversaw navy drills in Russia’s far east, come as the EU tries to ratchet up pressure on Russia’s so-called shadow fleet, expanding sanctions against hundreds of vessels and detaining some ships and their crews for checks. Some European governments have said they are exploring tougher maritime enforcement measures against ships suspected of sanctions evasion.

“We can see that the authorities of certain countries, in violation of international maritime law, are attempting to restrict the movement of our economic operators’ vessels … and have recently gone so far as to consider the possibility of seizing our vessels and selling off the property they have plundered from us,” Putin said.

“Naturally, this is nothing less than piracy and robbery. And if this begins to be put into practice, we shall be forced to respond in kind. And not necessarily in those waters where raids on our ships and vessels are planned, but wherever we ourselves deem it necessary and appropriate.”

Russia Accuses West of Operating Its Own ‘Shadow Fleet’

Viktor Liina, commander of Russia’s Pacific Fleet, told Putin that what he described as hostile countries such as Britain and France also transported goods on vessels flying flags of convenience which — if the EU and Britain’s own language was used — could also be described as a “shadow fleet.”

“Western states are actively using vessels flying the flags of third countries to transport cargo in their own interests. In essence, this constitutes their shadow fleet,” Liina told Putin.

“We have the capabilities to inspect and detain vessels belonging to unfriendly states and their shadow fleet; inter-agency coordination is in place, and we are ready to tackle these tasks.”

He said his fleet had carried out a detailed analysis of maritime traffic in the Asia-Pacific region and knew the routes, the cargo, and ownership of vessels linked to unfriendly nations.

The Russian Foreign Ministry weighed in too, accusing the EU in a statement of using its naval force in the Mediterranean — named operation EUNAVFOR MED Irini and originally launched to enforce a U.N. arms embargo on Libya — of carrying out unlawful inspections of foreign vessels.

It cited a search operation led by Italy that boarded a tanker from Russia’s so-called “shadow fleet” this month, the second such operation in less than two weeks as Europe intensifies scrutiny of vessels suspected of helping Moscow circumvent oil sanctions.

“Operation Irini is effectively being used by the European Union to intimidate commercial shipping companies and impede freedom of navigation. There is a clear abuse of existing international legal norms and an expansive interpretation of its powers,” the foreign ministry said.

“By resorting to such actions, the European Union is … bringing great dangers upon itself.”

(Reporting by Reuters; Writing by Andrew Osborn; Editing by Chizu Nomiyama and Keith Weir)