Tensions escalated late Sunday as Ukraine accused Russia of attacking its navy near Crimea.

Russian warships opened fire on a group of Ukrainian military vessels that previously tried to enter the Kerch Strait near the disputed peninsula, Ukraine’s Navy said on Facebook. Two men were wounded as the Russians “fired to kill,” according to the statement. Ukraine said three of its ships were captured.

Ukrainian President Petro Poroshenko called an emergency cabinet meeting for 10 p.m. local time and is in contact with the European Union and NATO over possible sanctions for what he called “criminal acts.” Poroshenko instructed the Foreign Ministry to inform the Group of Seven and the United Nations Security Council of the events.

While Russia didn’t confirm or deny using weapons, the Federal Security Service, or FSB, in Crimea said all necessary measures were used to stop the Ukrainians, according to the RIA news service. Commenting on Facebook, Russian Foreign Ministry spokeswoman Maria Zakharova called the events a “provocation” and accused Ukraine of setting it all up to accuse Russia of aggression.

Ukraine says it warned Russia in advance of the passage of its vessels through what are international waters. Russia, which annexed Crimea from Ukraine in 2014, defended its actions, saying the Ukrainian warships sailed into its territorial waters and were carrying out “dangerous maneuvers,” the Tass news service reported, citing the FSB. It said the Kerch Straits had been closed for security reasons.