Updated

Ukraine's leader lobbied the nation's NATO allies on Thursday “to assist Ukraine and provide security” by deploying ships to the Sea of Azov, where the country is embroiled in a tense standoff with Russia.

President Petro Poroshenko, who implemented martial law across Ukraine’s border region for 30 days earlier this week, said Russia “wants nothing less but to occupy the sea [of Azov].”

“The only language he understands is the unity of the Western world,” Poroshenko said in an interview with the German daily Bild published Thursday. “Germany is one of our closest allies and we hope the states within NATO are now ready to relocate naval ships to the Sea of Azov in order to assist Ukraine and provide security."

The tense stalemate between the two nations – ongoing since Russia’s annexation of the Crimean Peninsula in 2014 – escalated Sunday when the Russian coast guard reportedly fired on and seized three Ukrainian vessels and crews as the ships sought to pass from the Black Sea into the Sea of Azov through the Kerch Strait.

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Ukraine has insisted its vessels were operating in line with international maritime rules, while Russia said they failed to get permission to pass.

“We have all the evidence on the table, everyone can see that it was Russian soldiers who attacked our Navy,” Poroshenko told Bild. “We had to react after this act of aggression and that’s why I have decreed martial law in some regions because we need to protect our country. It’s like 2014: Putin wants to annex another part of Ukraine, he behaves exactly as he did then.”

Meanwhile, Russia insisted the Ukrainian vessels were in its territorial waters and refused to communicate with the Russian coast guard or accept a Russian pilot to guide them through the narrow strait.

"What were the border guards supposed to do?" Russian President Vladimir Putin said Wednesday. "They fulfilled their duty to protect the territorial integrity of the Russian Federation. If they had done something differently, they should have been put on trial for that."

There was no immediate reaction from German or NATO officials to Poroshenko’s request. While NATO condemned the Russian action, the allies will be unlikely to heed Poroshenko's request, which could trigger a confrontation with Russia. A 2003 treaty between Russia and Ukraine stipulates that agreement from each of the two littoral countries is required for warships from any other country to enter the internal sea.

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Putin, for his part, criticized the West for what he described as connivance with Ukraine's "provocation."

"The authorities in Kiev are successfully selling anti-Russian sentiments as they have nothing else left to sell," he said. "They can get away with whatever they do. If they want to eat babies for breakfast today, they will likely serve them too."

Poroshenko responded by ordering martial law in much of the country, a move that went into effect with parliamentary approval. Putin accused his Ukrainian counterpart of provoking the naval incident as a pretext to introduce martial law in a bid to shore up his sagging popularity and sideline competitors ahead of the March election.

The Associated Press contributed to this report.