Russian President Vladimir Putin began receiving information about the Ukrainian vessels near the Kerch Strait as soon as they appeared in neutral waters not far from Crimea, Kremlin spokesman Dmitry Peskov said.

"The president was informed about the movement of vessels immediately after they appeared in neutral waters opposite Crimea yesterday afternoon, and then he received information on a continual basis," Peskov told journalists on Monday.

Asked to comment on the future of the vessels and crews detained by the Russian border guard, Peskov said, "You and I know that a criminal case has been opened over the violation of the Russian Federation's border. I don't know the details."

Asked whether Putin himself made the decision to attack the Ukrainian vessels, Peskov replied, "This was not an attack, but actions necessary to prevent the violation of Russia's state border."

"Border guards have a scenario in this regard, which they follow in such situations," he said.