There have been standoffs between Ukrainian and Russian soldiers in Crimea. Nato has weighed in on calls from the US and Europe for a de-escalation of tensions.
Reports from the ground suggest that Russian troops in Ukraine have remained in the Crimea, and not pushed deeper into other regions of Ukraine.
However, at military bases in Crimea there have been standoffs between Russian and Ukrainian soldiers after Russians asked Ukrainian soldiers to hand over their arms. In some barracks, Ukrainians refused.
#Ukrainian marines in their base in #Perevalnoe – commander negotiating deal with #Russian troops outside. #Crimea pic.twitter.com/Mc6LHCe9Xi
— Lindsey Hilsum (@lindseyhilsum) March 2, 2014
Reports from the ground state that several roads and barracks in the Crimea have been blockaded.
The Nato Secretary-General has said that Russia is threatening peace and security and Europe. The foreign ministers of France and Britain have said they will pull out of preparatory G8 meetings in protest at Russia’s invasion of Ukraine.
And in a phone call on Saturday night, US President Barack Obama asked President Putin of Russia to pull his soldiers back to bases in the Crimea.
But responses from the West have not yet gone beyond political and economic threats. Mr Obama said the invasion would result in economic isolation for Russia and that he is consulting with other countries in Europe and NATO about what action to take.
The Russian president has gained permission from his government to invade Ukraine and according to reports on the ground has mobilised up to 6000 Russian troops already inside Ukraine.
Mr Putin cited concerns about Russians living in Ukraine and instability in the county as a justification for invading.
Analysis by Lindsey Hilsum: Why the trouble in Ukraine has only just begun
Negotiation through the UN or the Organization for Security and Cooperation in Europe was the correct way to address concerns about ethnic Russians in the Ukraine, Obama said.
Russia’s actions would lead to greater economic and political isolation, Mr Obama warned. He said he would be consulting with allies in NATO and Europe about the Russian invastion.
Inside Ukraine, the interim government has put all the country’s military assets on full alert, and asked for international monitors to enter the country to ensure that the country’s nuclear assets are not taken. Ukraine has closed its airspace to civilian aircraft.
Analysis by Paul Mason: Will a Russian invasion of Ukraine push the west into an economic war?