European Council President Donald Tusk on Monday condemned Russia's seizure of Ukrainian navy vessels in the Kerch Strait.
"I condemn Russian use of force in the Azov Sea. Russian authorities must return Ukrainian sailors, vessels and refrain from further provocations," Tusk said after a phone call with Ukrainian President Petro Poroshenko.
"Europe will stay united in support of Ukraine."
Three Ukrainian naval vessels seized by Russia off the coast of Russia-annexed Crimea on Sunday are being held at the Black Sea peninsula's port of Kerch, witnessed said on Monday.
Three Ukrainian ships seized by Russia are moored at Crimean port of Kerch