Three Ukrainian navy vessels, and a Russian patrol ship off the coast of Crimea on the morning of November 25, 2018. ©  Courtesy of FSB

Russian Federal Security Service (FSB) says three Ukrainian navy vessels, which crossed the marine border on Sunday morning, are heading for Kerch strait that separates Crimea from mainland Russia.

“This morning at around 7 a.m. Moscow time, three vessels belonging to Ukrainian armed forces violated the United Nations Convention on the Law of the Sea to enter Russian territorial waters,” read a statement from Russia’s federal security agency FSB, which is responsible for maintaining the country’s borders.

It said that the ships are heading for the Crimea Bridge, but have made no application to pass under it.

The vessels are undertaking dangerous maneuvers, and are not obeying lawful instructions from the Russian authorities.