The conflict pitting Ukrainian soldiers against Russian-backed separatists in the breakaway Donbas region, in eastern Ukraine, has sputtered along for nearly five years with more than 10,000 people killed. (Supplied) One of the three captured Ukrainian sailors shown on Russian state TV in front of a seized naval ship.
The UK condemned Russia's "destabilising behaviour in the region and its ongoing violation of Ukrainian territorial sovereignty".
"Russian coastguard vessels ... carried out openly aggressive actions against Ukrainian navy ships", Ukrainian authorities said in a statement, revealing that the tugboat's engine, hull, railings, and lifeboat were damaged in the incident. "Ready at any moment for an immediate invasion of Ukraine".
Russian Federation and Ukraine blamed each other in the dispute that ratcheted up tensions that have simmered since Moscow annexed Crimea in 2014 and threw its weight behind separatists in eastern Ukraine with clandestine support, including troops and weapons.
The Ukrainian parliament late on Monday (Nov 26) voted in favour of President Petro Poroshenko's request for the introduction of martial law in parts of the country for 30 days.
On Sunday, Poroshenko convened a military cabinet emergency meeting and later tweeted he would appeal to Parliament to declare martial law. Poroshenko's approval ratings have been plunging, and there were concerns that he would postpone a presidential election scheduled for March. The ships were headed north from Odessa to Mariupol on the Sea of Azov.
The naval clash is one of the most significant events in Ukraine and Russia's hostilities since the Russian annexation of Crimea in 2014, potentially setting up further conflict if tensions aren't brought under control.
On Monday, Nikki Haley, the USA ambassador to the U.N., called the incident an "outrageous violation of sovereign Ukrainian territory" and "another reckless Russian escalation" during an emergency meeting of the U.N. Security Council.
Poroshenko's call also outraged far-right groups in Ukraine that have advocated severing diplomatic ties with Russian Federation.
Russia has so far resisted calls to release them, accusing the sailors of crossing illegally into Russian waters and of ignoring warnings from its border guards. They attempted to do so by the only possible way to go, through the Kerch Strait.
On Tuesday, the country's state security service announced that its intelligence officers were among the crew on Ukrainian naval ships seized by Russian Federation.
While other USA officials took a strong stand behind Ukraine, President Donald Trump seemed more equivocal.
North Atlantic Treaty Organisation ships are allowed into the Black sea for a limited time and without heavy weapons.
"These were targeted actions, with engagement of necessary aviation, electronic warfare, assault forces, special forces", the president commented on a recent incident when Ukrainian boats were attacked and captured by Russian forces near the Kerch Strait in the Black Sea.
"It's not a political issue here, because we can have an argument about the legal status, but it's about simply concentrating on protecting them and helping them", Foreign Minister Pavlo Klimkin told the AP. In a brief statement Monday afternoon, he told reporters: "We do not like what's happening, either way, we don't like what's happening and hopefully it will get straightened out".
Earlier, the Russian envoy to the United Nations, Dmitriy Polyanskiy, said at a November 26 UN Security Council emergency session in NY that two SBU officers had been on board one of the Ukrainian military vessels trying to enter the Sea of Azov through the Russian-controlled Kerch Strait.