The FSB accused the Ukrainian navy of staging a provocation against Russian Federation. "[The Russians] shoot to kill", the press service of Ukraine's Navy said on Facebook at 20:28 local time on November 25.
Russia's coast guard said that three Ukrainian navy ships made an unauthorized crossing through Russian territorial waters, while Ukraine alleged that one of its boats was rammed by a Russian coast guard vessel.
Russia's Federal Security Service (FSB), meanwhile, says Kyiv "illegally" entered its territorial waters and carried out "dangerous manoeuvres" against the orders of Russian authorities, prompting them to act.
According to the Ukrainian navy, the naval vessels Berdyansk, Nikopol and Yani Kapu were carrying out a planned transfer from the port of Odessa to the port of Mariupol on the Azov Sea.
The Kerch bridge is seen blocked for ships entrance, near Kerch, Crimea, Sunday, Nov. 25, 2018.
Moscow on Sunday placed a large cargo ship beneath the 19km-long Crimean Bridge, which connects the Russian-annexed peninsula with its mainland, blocking all traffic into the strait, the only passage into the Sea of Azov.
RQ-4 Global Hawk
The Ukrainian navy said the flotilla was continuing its journey regardless. The move comes after months of growing tensions between Ukraine and Russian Federation, which annexed Crimea from Ukraine in 2014 and has steadily worked to increase its zone of control around the peninsula.
Russian Foreign Ministry spokeswoman Maria Zakharova said on Facebook that the incident was characteristic of Ukrainian behavior: provoke, pressure and blame for aggression.
A spokesman for Ukrainian President Petro Poroshenko said Kyiv was convening an emergency meeting of the military's top brass on Sunday night after the second incident in a tense standoff between the two foes.
"Their goal is clear", an FSB statement said, "to create a conflict situation in the region".
Ukraine accused a Russian coastguard vessel, named the Don, of ramming one of its tugboats in "openly aggressive actions".
Kyiv said Moscow had violated the UN Convention on the Law of the Sea and the contract between Kiev and Moscow on the use of the Sea of Azov and the Kerch Strait.