Ukraine said six sailors had been injured on Sunday, in what it described as an attack by jet fighters. The country's defense ministry has since announced orders to put the military on full combat readiness.
Ukraine accused Russian navy vessels of illegally trying to intercept their ships, ramming its tug boat in the process. It added their vessels attempted to continue towards the Kerch Strait, which is the only access they have to the Sea of Azov, but were eventually thwarted by a Russian tanker placed underneath a bridge.
"Politically, Russia is interested in sowing disarray in Ukraine and aims to undermine the incumbent president in his attempts to be re-elected in 2019," Orysia Lutsevych, a research fellow with the London-based Chatham House think tank, told CNBC via email on Monday.
"This act of aggression is testing the resolve and capabilities of Ukrainian Armed Forces to defend territorial integrity of Ukraine," Lutsevych said.
Russia's FSB confirmed one of its patrol boats had used force to seize three Ukrainian shipping vessels but claims only three sailors were injured in the process.
Russia's foreign ministry said Monday that Ukraine had most likely planned the incident in advance, accusing its neighbour of trying to provoke a reaction. Maria Zakharova, a spokesperson for Russia's foreign ministry, told state television a senior Ukrainian diplomat would be summoned to discuss the standoff, according to Reuters.
The Kerch Strait was re-opened by Russia in the early hours of Monday morning.