MOSCOW: President Vladimir Putin signed on Tuesday a treaty claiming the Black Sea region of Crimea as Russian territory, as Ukraine warned the showdown had entered a ‘military stage’ with the killing of one of its soldiers on the peninsula.

The treaty signing was conducted at lightning speed in the Kremlin in a defiant expansion of Russia’s post-Soviet borders that has plunged relations with the West to a new post-Cold War low.

The move, less than three weeks after pro-Moscow troops first seized control of the strategic peninsula, triggered furious condemnation from Western leaders.

Ukraine said one of its soldiers had been killed in Crimea on Tuesday, the first confirmed fatality on the peninsula, and interim President Oleksandr Turchynov accused Russia of acting like “Nazi Germany”.

The West, which backs the new leaders in Ukraine who took power after last month’s ousting of pro-Moscow president Viktor Yanukovych, condemned Moscow’s actions as a blatant annexation of Crimea.

US Vice President Joe Biden bluntly accused Russia of a ‘land grab’ and German Chancellor Angela Merkel said the move was against international law.

Putin signed the treaty with Crimean prime minister Sergei Aksyonov and other Crimean leaders at a ceremony at the Kremlin attended by both houses of parliament, after over 97 per cent of Crimeans voted in favour of joining Russia in a disputed referendum on Sunday.

Russian lawmakers, who still have to formally ratify the treaty although it comes into force immediately, broke into raucous applause and cheers after the signing.

“The Republic of Crimea is considered to be part of Russia from the date of the signing of the treaty,” the Kremlin said.

Crimea and the city of Sevastopol – the home of the Russian Black Sea fleet which has special status – are being incorporated as new constituent parts of the Russian Federation.

“We’ve waited for this moment for many years,” said a jubilant Anatoly Volkovoi, 70, in Crimea’s main city of Simferopol.

The signing – which had not been flagged in advance – came after Putin gave a fiery address at the Kremlin seeking to justify the incorporation of Crimea into Russia.

His defiant speech referred to Crimea’s ancient and Soviet history and brushed off US and EU sanctions touted by US officials as the most severe against Moscow since the end of the Cold War.

“In the hearts and minds of people, Crimea has always been and remains an inseparable part of Russia,” Putin said.

He said Crimea belonged with Russia and he slammed the Soviet-era decision by Nikita Khrushchev to gift the peninsula to the Ukrainian Soviet republic as riddled with “violations”.

“When Crimea suddenly ended up being in another state, Russia felt it was not simply robbed – it was plundered,” he said.

He added that Russia was tired of being pushed into a corner by the West and said it had been repeatedly deceived on issues like Nato, missile defence and visa-free travel.

“On Ukraine the West crossed a line,” he said, warning it against provoking Russia.

However, he sought to play down fears that Russia was seeking to also incorporate parts of eastern and southern Ukraine, whose Russian-speaking population are far from supportive of the new authorities in Ukraine.