Russian President Vladimir Putin has accused Ukraine's leader, Petro Poroshenko, of trying to boost his ratings ahead of 2019 elections with a naval confrontation off Crimea.
Russian FSB border guards opened fire on two Ukrainian gunboats and a tug before seizing the Ukrainian crews.
"He had to do something to make the situation more tense," Mr Putin told an investment forum on Wednesday.
Ukraine has condemned the incident as a Russian "act of aggression".
The EU has expressed "utmost concern about the dangerous increase of tensions" and said Russia's use of force was "unacceptable", but did not mention any new sanctions.
At least three of the Ukrainian sailors were wounded on Sunday as tensions spilled over near in the Kerch Strait, the passage between the Black Sea and the Sea of Azov off the coast of Crimea.
The peninsula was seized from Ukraine in 2014 and annexed by Russia shortly afterwards.