Ukraine's president has sought to gain support from NATO states in his stand-off with Russia after the clash in the Sea of Azov off the Crimean coast.
"Germany is one of our closest allies, and we hope that states within NATO are now ready to relocate naval ships to the Sea of Azov in order to assist Ukraine and provide security," President Petro Poroshenko told Germany's Bild daily, suggesting Russia "wants nothing less than to occupy the sea."
Naming German Chancellor Angela Merkel as a great friend of Ukraine, Poroshenko said that "in 2015, she already saved our country with her negotiations in Minsk, and we hope she will once again support us so strongly, together with our other allies."
Poroshenko suggested that Russia and its president, Vladimir Putin, had major plans.
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"Putin wants to bring back the old Russian Empire. Crimea, Donbas, he wants the whole country," Poroshenko suggested. "As a Russian emperor, as he sees himself, his empire cannot function without Ukraine, he sees us as a colony."
For his part, Putin accused Poroshenko on Wednesday of orchestrating a "provocation" to boost his flagging popularity ratings before an election next year. The latest opinion polls in Ukraine show only 9 or 10 percent support for the Ukrainian president.
Putin defended his forces' actions in seizing three Ukrainian ships last weekend in the Sea of Azov: "They were fulfilling their military duty," he said. "They were fulfilling their lawful functions in protecting Russia's borders."
Poroshenko has imposed martial law in parts of Ukraine for 30 days.
EU makes a statement
The EU's top diplomat, Federica Mogherini, on Wednesday night issued a statement expressing "utmost concern about the dangerous increase of tensions" and dismay at the "unacceptable" use of force by Russia. It called on Russia to release the Ukrainian vessels and sailors it seized and ensure unrestricted sea access.
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There was no mention of sanctions in the statement. The bloc is divided on imposing further measures against Moscow. Countries such as Italy, Greece, Belgium and Cyprus have been calling for a softer approach to Russia, as Germany and France have focused on measures to ease tensions. Only the three former Soviet states on the Baltic Sea — Estonia, Latvia and Lithuania — backed by Poland and the UK called for tougher language against Moscow.