Tensions on the Crimean Peninsula soared yesterday after President Vladimir Putin put the Russian Army on high alert and Nato officials warned they would back the "inviolability of [Ukraine's] frontiers".

Last night pro-Russian armed men seized control of the regional Parliament and government buildings in Simferopol, Crimea, raising Russian flags above them. Up to 50 men with weapons marched into the buildings, hoisted Russian flags on top and were blocking government workers from entering, Crimean Prime Minister Anatoliy Mohilyov said. Local authorities would "take measures", Mohilyov said.

The flurry of sabre-rattling over the future of Ukraine brought tensions between Moscow and the West to a height not seen since the 2008 war between Russia and Georgia. There were unconfirmed reports that Viktor Yanukovych, the former President ousted from power by protesters last weekend and now wanted by Ukraine's authorities for mass murder, had taken refuge at a luxury sanatorium just outside Moscow. Sergei Shoigu, Russia's Defence Minister, ordered units in the western military district, which borders Ukraine, to begin a series of snap drills.

The drill would "check the troops' readiness for action in crisis situations that threaten the nation's military security", he said. It would involve about 150,000 army, air force and navy personnel. Moscow also said it was "carefully watching what is happening in Crimea", taking measures to ensure the security of the facilities and arsenals of its Black Sea naval fleet, based in Sevastopol.


John Kerry, the US Secretary of State, quickly responded by warning Russia "to be very careful in the judgments that it makes", adding: "we are not looking for confrontation. But we are making it clear that every country should respect the territorial integrity here, the sovereignty of Ukraine. Russia has said it would do that and we think it's important that Russia keeps its word."

He reiterated that the US does not view its relationship with Russia as a "sort of continuation of the Cold War", adding "this is not Rocky IV". The 1990 film depicted a battle between East and West, in which Rocky Balboa fights then-Soviet Union boxer Ivan Drago.

Nato defence ministers warned they considered Ukraine's future to be "key to Euro-Atlantic security" and assured the new Government in Kiev that the alliance would back its "sovereignty, independence [and] territorial integrity".

"A sovereign, independent and stable Ukraine, firmly committed to democracy and the rule of law, is key to Euro-Atlantic security," their statement said.

The comments appear to be a direct response to comments by high-ranking Russian officials, including Dmitry Medevedev, the Prime Minister, who said this week that the revolution in Ukraine posed "a real threat to our interests".

While many throughout Ukraine see the revolution as an uprising against a corrupt and discredited elite, Russian-speaking Ukrainians and ethnic Russians are alarmed by what they see as nationalist and Russophobic elements among the groups that have seized control in Kiev.

Russia has warned it may act to protect its citizens in the Russian-majority region of Crimea, where it maintains a naval base and a 25,000-strong garrison.

The new Government in Kiev continued to consolidate its grip on power yesterday, with the Acting President, Oleksandr Turchynov, assuming command of the armed forces. Arseniy Yatsenyuk, a former Foreign Minister, was proposed as the country's new Prime Minister. A list of suggested Cabinet members was read out to the crowd in Independence Square. It will go before Parliament for confirmation today.

Parliament has disbanded the Berkut, a special riot police unit blamed for much of the previous violence against protesters. That move heightened fears in Russian-speaking parts of Ukraine. The anti-revolutionary Mayor of Sevastopol has promised to retain the unit as part of his municipal police force. At least one person died and seven were injured in a stampede after rival demonstrators clashed in Simferopol.

Radical policing at rubbery checkpoint

The task of controlling entry to a city of almost three million has fallen to a 30-year-old electrician called Andreiy, who mans a motorway checkpoint made of old tyres.

Along with four other revolutionaries clad in motley camouflage, he stands guard on the northeastern fringe of Kiev.

In the aftermath of the revolution, Ukraine's police have disappeared from the streets and handed their duties over to revolutionaries. In other capitals, the sudden withdrawal of the police would risk a general collapse of law and order. But Kiev is different: shops and offices have reopened and traffic fills the streets. Even banks and jewellers feel confident enough to open their doors.

Andreiy and his comrades keep watch for buses packed with "tituskhi" - the young criminals hired by the old regime to harass protesters. "If we see a suspicious vehicle, we take the registration number and contact the revolutionaries in the centre of Kiev and ask them to stop it. If they call us and tell us to stop a car, then we do."

The revolutionaries have shown their ability to enforce order. The central area which they have controlled for months is packed with expensive shops, including branches of Gucci and Louis Vuitton. These businesses have closed their doors, but their windows are unbroken and there is no visible sign of looting.