Ukrainian boats had attempted a provocation in the Sea of Azov a month before the Kerch Strait incident, according to a senior Russian naval official.
Two Ukrainian armoured gunboats, the Lubna and the Kremenchug, escorted a vessel carrying a Bulgarian flag from the Ukrainian port of Mariupol through the Kerch Strait, Vice Admiral Aleksei Volsky, first deputy head of Russia's FSB coast guards, told a briefing in Moscow on Saturday.
He went on to say that during the operation, the Ukrainian vessels threatened to use force against Russian coastguard ships and set their weapons on standby.
Volsky underlined that there had been no reports about Russian ships threatening Ukrainian gunboats and warships. There is "no doubt" that the construction of the Kerch Bridge (between Crimea and Krasnodar region) was the target of Ukraine's main provocations, he added, citing repeated claims from Kiev officials that the bridge should be destroyed.
Three Ukrainian Navy vessels — two gunboats and a tugboat — were seized on November 25 after violating Russian waters and sailing through the Kerch Strait, the entrance to the Sea of Azov. The ships failed to respond to demands to stop and made dangerous manoeuvres, the FSB said. A court in Simferopol issued a decision ordering that all of the 24 Ukrainian servicemen captured in the incident, including two SBU officers, be held in custody for two months.
Ukraine, in response to the seizure, introduced martial law for 30 days in the regions of the country bordering Russia, the Black Sea and the Sea of Azov. Additionally, Ukrainian President Petro Poroshenko announced that Ukraine would ban Russian males aged 16-60 from entering the country.
Russian President Vladimir Putin described the manoeuvres as a "provocation" that was likely intended as a pretext to introduce martial law in Ukraine and boost Poroshenko's low approval ratings ahead of the March 2019 presidential vote. Kiev claims that the operation was meant to demonstrate the capabilities of Ukrainian vessels.