Russian leader Vladimir Putin on Tuesday (18 March) signed a treaty annexing the Ukrainian region of Crimea, shortly before the Russia-Ukraine confrontation claimed its first casualty.

He justified the step in a long speech to MPs which described the Black Sea peninsula - given by the USSR to Ukraine in 1954 - as quintessentially Russian in cultural and historical terms.

Student or retired? Then this plan is for you.

Putin with Crimean separatist leaders in Moscow on Tuesday (Photo: kremlin.ru)

He said Ukraine is now run by “neo-Nazis, anti-Semites, and Russophobes.”

He also framed the crisis in a geopolitical context, accusing Western powers of trying to stop him from creating a Eurasian Union by orchestrating “controlled” revolutions.

“We understand what is happening, that these actions were directed against Russia and against integration in Eurasia … But everything has its limits. And in the case of Ukraine, our Western partners crossed the line, they were rude, irresponsible.”

With Russia’s ratification of the Crimea treaty to be completed in the next few days, the annexation looks like a fait accompli.

But there are fears Putin will go further.

He noted in his speech that ethnic Russians in the Ukrainian cities of Donetsk, Kharkiv, and Kiev are “still” appealing for his help and he described Kiev as the “mother of all Russian cities," adding: "Ancient Rus is our common source and we cannot live without each other.”

He has amassed military forces on Ukraine's north and eastern borders.

If he is going to absorb Crimea, he will also need to take control of the electricity and water infrastructure which feeds it and which is located on the Ukrainian mainland.

Shortly after Putin stopped talking, the Ukrainian PM, Arseniy Yatsenyuk, accused Russian forces of shooting dead a Ukrainian officer at a base in the Crimean capital of Simferopol.

He called for a meeting with UK and US defence chiefs and said the crisis has entered a “military stage.”

For his part, Ukraine’s former president, Viktor Yushchenko, told EUobserver in an interview in Brussels the same day: “He [Putin] is a maniac who is obsessed with the idea of recreating the Soviet Union and, sadly, he is not the only one like this in the Russian political establishment.”

The former commander-in-chief praised the Ukrainian army's restraint, but said that if it comes to war, then Russia has “underestimated” its opponent.

“Our army is technologically advanced, very professional, and highly educated. We have the same types of weapons the Russians have … and a very strong spirit."

EU countries and the US also reacted to Tuesday’s developments with strong words.

US vice-president Joe Biden, while visiting Warsaw, said the US will impose extra sanctions on top of its earlier blacklist of Russian officials and MPs: “Russia is alone. It’s clear that Russia’s economic isolation will increase if it stays on this path."

British foreign minister William Hague tweeted: “preparatory work now underway for a third tier of [EU] sanctions, including economic & trade measures.”

EU Council chief Herman Van Rompuy and European Commission head Jose Manuel Barroso also said EU leaders at a summit on Thursday will “agree on a united European response.”

Meanwhile, a European Parliament committee named 32 Russians who it says should be on an EU blacklist for their role in murdering a Russian anti-corruption campaigner, Sergei Magnitsky.

With MEPs voting 53 to one in favour, the move, albeit symbolic, indicates the mood in the EU capital.

Punitive measures aside, Yushchenko added that the “biggest sanction” the EU and US could impose on Putin would be economic and political support for Ukraine.

He listed a clear EU and Nato membership perspective and EU visa-free travel as the most important elements.

He also warned the West that all may not be as it seems in Ukraine.

Reports in some Russian media say that Yushchenko's old rival, former PM Yulia Tymoshenko, cut a deal with Putin - to give him Crimea in return for helping her to regain power.

She told EUobserver earlier this month it is "anti-Ukrainian propaganda."

But Yushchenko said it is “quite strange” that Ukraine's Tymoshenko-dominated government has done nothing to secure the Crimean electricity and water infrastructure on the mainland. He said it is equally strange Ukraine did not close its border with Russia to stop Russian agitators from going to Donetsk and Kharkiv.

“I belong to this group of people [who believe there is a Putin-Tymoshenko deal],” Yushchenko said.

“This is one of the biggest mysteries for Europeans … The line of relations between these two people have been significantly underestimated and Europe risks falling into their traps,” he added.