Speaking on a visit to a Russian warship that was taking part in a naval exercise in the Pacific, Putin described the Western moves to detain vessels linked to Russia as a breach of international maritime law.
"It's nothing but piracy and robbery," Putin said on Wednesday.
"If this is done, we will be forced to respond in kind."
He said the Russian response would not necessarily go in the waters where the Russian ships were seized, noting that Moscow could retaliate "in any area where we see it as necessary and appropriate", including in the Pacific.
The Pacific Fleet chief, Admiral Viktor Liina, reported to Putin that the navy was ready to start inspections of the commercial ships serving the "unfriendly nations".
He noted that many of the ships operated by British, French and other European carriers fly the flags of other nations, effectively making them a "shadow fleet".
"We have enough assets for inspection and detention of vessels of the unfriendly nations and their shadow fleet," Liina told Putin.
"We are ready to start performing the task."
Russia is believed to be using a fleet of hundreds of ships to evade international sanctions imposed after Moscow sent troops into Ukraine in February 2022.
France and the UK have detained tankers suspected of being of Russia's "shadow fleet" shipping oil in violation of international sanctions.
The EU has sanctioned hundreds of "shadow fleet" ships.
Russia has recently started deploying warships to escort its commercial vessels.
Dmitry Medvedev, who served as Russia's president in 2008-12 to let Putin observe term limits and is now deputy head of Russia's Security Council, noted that many ships belonging to European carriers flew the so-called "flags of convenience" just like Russian carriers did.
"It means that by applying a symmetrical approach, which is only fair, Russia has the right to attack any merchant vessel belonging to hostile nations, whether in our waters or in neutral waters, provided there are reasonable grounds to suspect it is carrying cargo in the enemy's interest, and that applies to any cargo," Medvedev said.
"There are a great many such vessels, and our military is capable of dramatically expanding operations well beyond the Black Sea basin."
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