Another Russian 'shadow fleet' tanker has been boarded by European forces - and this time the provocative action took place in Mediterranean waters. In a Monday post on X, Kaja Kallas announced the action by troops under the EU's Operation Irini. They boarded the MV Sun tanker for "flag verification," following suspicions that the vessel was in violation of international law.

"Illegal oil sales from shadow fleet ships are a critical lifeline for Russia’s war in Ukraine, and we’ll continue to cut them off," Kallas wrote of what marks the sixth shadow fleet ship to be boarded in recent months. Most of these have happened in northern European waters, with Mediterranean incidents being more rare.

It was specifically the Italian Defense Ministry that carried out the EU action, with Italian navy's Thaon di Revel ship conducting the boarding which occurred to the west of the island of Pantelleria as the targeted vessel was progressing from the port of Cotonou in Benin to Istanbul.

Russian President Vladimir Putin just a little over two weeks ago threatened to do the same in reverse, after the past year saw several examples of EU intercept action, sometimes involving French or Swedish commandos descending onto a tanker's deck from helicopters and arresting crew members. The seized vessels are then typically taken to nearby European ports.

The latest European Union sanctions package passed last month stipulates that EU members can sell the oil or any seized cargo obtained from these 'shadow fleet' vessels.

Putin has reiterated Kremlin outrage at this scheme, condemning it as "piracy and banditry". This also after Sweden has lately declared its intent to hand seized Russian grain over to Ukraine.

"We will be forced to respond in kind," Putin said in mid-August. Russian forces will act "wherever we ourselves deem necessary and appropriate — anywhere," he added.

According to more of what Putin threatened at the time, as translated and presented in Reuters...

"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."

But so far this has yet to happen, other than major Russian military action in the Black Sea, which has chiefly targeted Ukrainian imports, as well as southern Ukrainian ports.

So while Russia would not likely act in European waters, such a scenario would be more likely to go down in places like the Black Sea or Baltic region, or perhaps the faraway Indian Ocean. Still, Putin's patience is likely wearing very thin.