Acted within international law in Kerch Strait: Russia
"The Russian side acted strictly within both domestic and international law," Kremlin spokesman Dmitry Peskov said during a daily press briefing.
"We are talking about the intrusion of foreign military ships into Russian territorial waters," he said.
He said President Vladimir Putin was informed when the Ukrainian ships entered "neutral waters in front of Crimea" on Sunday afternoon and that he was briefed on an "ongoing basis".
Peskov said Russia's actions were not "an attack, but necessary actions to prevent the crossing of Russia's borders."
The confrontation at sea has raised fears of a wider military escalation and the UN Security Council was to hold an emergency session later Monday to consider a response.
(With inputs from agencies.)