Russian President Vladimir Putin has warned that Moscow will retaliate in kind should European nations begin seizing Russian commercial ships, while the commander of Russia's Pacific Fleet stated his personnel stand prepared to "inspect and detain" foreign boats.

Speaking while supervising naval exercises in eastern Russia, Putin issued the warning as the European Union steps up action against Moscow's covert shadow fleet, broadening sanctions to encompass hundreds of vessels and stopping individual vessels alongside their crews.

A number of European states have confirmed they are considering stricter maritime intervention protocols to target vessels believed to be circumventing trade sanctions.

"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," said Putin.

"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."

Viktor Liina, commander of Russia's Pacific Fleet, told Putin that what he described as hostile countries like 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 the vessels. Putin also accused NATO of threatening behaviour in the Asia-Pacific region, and of creating tension in the Arctic.

"We can see that, unfortunately, the potential for conflict is growing here; NATO is making inroads here; new military-political blocs are being formed; and new weapons systems are being deployed here, or are planned for deployment, which also pose a threat to our country," said Putin.