Russia's military intervention in Ukraine
Crimean and Russian Cossack volunteers who arrived to help local police, stand in formation in the Crimean port city of SevastopolReuters

Russian Prime Minister Dmitry Medvedev has said the latest crisis in neighbouring Ukraine, which culminated in the removal of Viktor Yanukovich, will end in fresh bloodshed with the overthrow of Ukraine's interim government.

Amid the Russian military build-up which has sparked widespread condemnation, Medvedev denounced the "seizure of power" by the Ukrainian authorities.

In a post on his official Facebook account, the Russian leader said: "If he is guilty before Ukraine - hold an impeachment procedure ... and try him. Everything else is lawlessness. The seizure of power."

He adds: "And that means such order will be extremely unstable. It will end in a new revolution. New bloodshed."

The Russian parliament has authorised President Vladimir Putin for armed intervention in Ukraine in order to protect Russia's interests in the country.

Medvedev continued: "Russia is ready to develop multi-faceted, respectful relations with brotherly Ukraine - mutually beneficial and effective relations. But Ukraine for us is not a group of people who, pouring blood on the Maidan [Kiev's Independence Square], seized power in violation of the constitution and other state laws. Russia needs a strong and stable Ukraine. A predictable and economically thriving partner. Not a poor relation that's always standing with a hand held out."

There are clear signs of preparations for an invasion in Ukraine's semi-autonomous and pro-Russian region of Crimea, where Moscow's forces are believed to have total control.

Most of the Ukrainian units stationed in Crimea, which has a majority of ethnic Russians, have already sided with the pro-Russian forces, suggest local reports.

Crimean Prime Minister Sergei Aksenov said: "I would like to warn commanders who force their subordinates to commit illegal actions that they will be punished according to existing laws."

The latest escalation of the crisis has evoked a strong response not only from Ukraine's interim officials, who condemned Russia's "open declaration of war", but also from Russia's partners in the G8.

The group has said they are halting all preparations for the planned international summit in Russia.

A White House statement said: "We, the leaders of Canada, France, Germany, Italy, Japan, the United Kingdom and the United States and the President of the European Council and President of the European Commission, join together today to condemn the Russian Federation's clear violation of the sovereignty and territorial integrity of Ukraine."

"We have decided for the time being to suspend our participation in activities associated with the preparation of the scheduled G8 Summit in Sochi in June."