Russia’s military build-up in Ukraine has been condemned by its G8 partners amid fresh diplomatic efforts to avert a dangerous escalation of the crisis.
The world’s seven major industrialized powers also suspended preparations for the G8 summit in Sochi in June.
Meanwhile, the EU foreign ministers are due to meet in emergency session in Brussels.
The moves come as Russian military forces continue to strengthen their grip on the Crimean peninsula.
Ukraine’s interim government has accused Russia of having declared war, and has ordered the mobilization of its armed forces.
Russian President Vladimir Putin has so far defied calls from the West to pull back his troops.
He insists Russia has a right to protect its interests and those of Russian-speakers in Crimea and elsewhere in Ukraine.
The UN said on Sunday that Deputy Secretary-General Jan Eliasson was travelling to Ukraine to be “personally apprised of the facts on the ground”.
A statement said he would brief UN Secretary General Ban Ki-moon “on the next steps the United Nations could take to support the de-escalation of the situation”.
On Monday morning, the MICEX index of stocks in Moscow suffered an initial fall of about 5% and the rouble fell 2.5% to an all-time low against the US dollar.
Russia’s central bank also raised its main interest rate to 7% from 5.5%.
The G7 of Canada, France, Germany, Italy, Japan, the UK and the US urged Russia to hold talks with Ukraine to address any human rights or security concerns it had.
In a statement released from the White House, the grouping said it condemned “the Russian Federation’s clear violation of the sovereignty and territorial integrity of Ukraine”.
It added: “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.”
G7 finance ministers said they were ready “to provide strong financial backing to Ukraine”.
“The International Monetary Fund [IMF] remains the institution best prepared to help Ukraine address its immediate economic challenges through policy advice and financing,” a statement said.
Ukraine needs $35 billion over the next two years, according to the finance ministry.
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