Following up on an overwhelming majority backing such a move in the weekend referendum, Russian President Vladimir Putin has signed a treaty formally annexing Crimea back into the Russian Federation. The treaty is expected to be ratified by Russian parliament in days, and by a similarly overwhelming margin.

Putin says the move marks Crimea’s return to “home port.” Crimea has traditionally been a part of Russia and was for centuries the home of its navy. Putin added that his government doesn’t seek annexation of any other regions within Ukraine, and that Crimea was a special case because it “remains an inseparable part of Russia.”

Ukrainian interim Prime Minister Arseniy Yatsenyuk loudly condemned the move, saying it moves the dispute over Crimea “from a political to a military stage.” Ukrainian officials have been hyping the mobilization of the military and the preparation for war with Russia.

A clash was also reported at one of Ukraine’s remaining military bases within Crimea, where unidentified fighters with covered faces stormed the base, killing one Ukrainian soldier and wounding another. Yatsenyuk dubbed the incident a Russian “war crime,” though officials concede there was no proof the Russian military was actually behind the attack, and defectors to the new Crimean military have been paritcularly aggressive in confronting the remnants of Ukraine’s forces in the area.

At the same time, Ukraine’s interim government tried to tamp down concerns it was becoming a NATO proxy along the Russian border, with the Foreign Ministry pledging never to join NATO and saying they want to improve ties with Russia.