"I want to emphasise separately that we have all irrefutable evidence that this aggression, this attack on the Ukrainian Navy's warships was not a mistake, not an accident, but a deliberate action," he said in a statement.

The United Nations Security Council is due to discuss the developments on Monday at the request of Russia, said Deputy Russian UN Ambassador Dmitry Polyanskiy.

The European Union said in a statement it expected Russia to restore freedom of passage via the Kerch Strait and urged both sides to act with the utmost restraint to de-escalate the situation.

German Foreign Minister Heiko Maas on Monday called Russia's blockade of access to the Sea of Azov "unacceptable" and urged an easing of tensions with Ukraine.

"The developments are troubling," he tweeted. "A Russian blockade of the passage to the Sea of Azov is unacceptable. It is important that the blockade be lifted. We call on both sides to deescalate."

About 50-100 people gathered outside the Russian Embassy in Kiev to protest against Moscow's actions. An embassy vehicle was set on fire, according to reports.

Russia seized Crimea in 2014 and strengthened its grip by building a road bridge connecting the peninsula to southern Russia across the Kerch Strait, a narrow stretch of water linking the Black Sea to the Sea of Azov, which is home to two of Ukraine’s most important ports.