A dispute between Ukraine and Russia in which each accuses the other of violating laws of the sea escalated sharply on Sunday when the Ukrainian Navy said the Russian military opened fire on several of its ships, wounding six sailors and seizing the vessels.
The incident in and around the Kerch Strait, a narrow body of water separating the Black and Azov Seas, marked a pivot in the undeclared war, now nearly five years old, between the former members of the Soviet Union.
The Ukrainian military has been fighting two separatist movements in eastern Ukraine that are clearly backed by Moscow, though the Russian government has formally denied any direct military intervention.
That is in contrast to Sunday’s events, which unfolded as a direct confrontation between Russia and Western-backed Ukrainian armed forces at sea.
The episode also threatened to shake up Ukraine’s fragile internal politics.
At a midnight meeting, Ukraine’s National Security and Defense Council said it would ask Parliament to declare a state of martial law. That raised alarms that President Petro O. Poroshenko could use the incident to delay a presidential election scheduled for March that polls suggest he is unlikely to win.
“This whole story grows more complicated by the fact that during martial law, it is forbidden to hold presidential, parliamentary or local elections, as well as strikes, protests, rallies and mass actions,” Mustafa Nayyem, a member of Parliament, posted on Facebook.
The Ukrainian Navy left little ambiguity in asserting that its ships had been attacked. “Fighter jets used weapons against the naval ships of the armed forces of Ukraine,” the navy’s statement said.
Russia’s Federal Security Service, a law enforcement agency known as the F.S.B. that oversees the Coast Guard, initially issued a statement saying the Ukrainian ships had, after an altercation, altered course to return to a Ukrainian port. But it later said that Russia had detained the vessels and that it was providing first aid to three sailors.
The F.S.B. said in statement carried by Russian news agencies that the Ukrainian naval convoy of two small warships and a tugboat had entered Russian territorial waters near Crimea on Sunday in a “provocation.” The Russian Coast Guard responded by trying to escort them out of the area, it said.
“Their goal is clear,” the F.S.B. said of the Ukrainian naval ships, “to create a conflict situation in the region.”
The Russian reports said the Ukrainian ships disregarded announcements that the Kerch Strait was temporarily closed.
The portion of the Black Sea where the confrontation unfolded is a swirl of contested borders and disputed rights to access through the strait. Read more