Russia insists its protecting its citizens in Ukraine
Russia has insisted troops that have streamed into Ukraine are protecting Russian citizens living there.
Foreign minister Sergey Lavrov said it is necessary to use Russian troops in Ukraine "until the normalisation of the political situation".
He told an opening session of the UN Human Rights Council in Geneva that Moscow is committed to human rights and added that "military interventions on the pretext of civilian population produce the opposite effect".
Ukraine has accused Russia of a military invasion, and has called on Kremlin to withdraw its troops.
Yesterday the Kiev administration put its military on high alert and appealed for international help to avoid what it fears is a possible wider invasion by Russia.
US secretary of state John Kerry also called on president Vladimir Putin to pull back from "an incredible act of aggression".
After Russia captured the Crimean peninsula without firing a shot, fears grew in the Ukrainian capital and beyond that Moscow might seek to expand its control by seizing other eastern parts of the country.
The US believes Russia has complete operational control of Crimea, a pro-Russian area of the country, and has more than 6,000 troops in the region.
Ukrainian prime minister Arseniy Yatsenyuk said there was no reason for Russia to invade and warned that "we are on the brink of disaster".
Pro-Russian troops have taken over a ferry terminal on the easternmost tip of Crimea, intensifying fears that Moscow will send even more troops.
The terminal in the Ukrainian city of Kerch is about 12 miles by boat to Russia.
Soldiers are operating the terminal, which serves as a common departure point for many Russian-bound ships.
The men refused to identify themselves, but they spoke Russian and the vehicles transporting them had Russian licence plates.
Tension between Ukraine and Moscow rose sharply after Ukraine's pro-Russian president Viktor Yanukovych was pushed out by a protest movement among people who wanted closer ties with the European Union.
Yanukovych fled to Russia after more than 80 demonstrators were killed near Kiev's central square, but says he is still president.
Since then, troops that Ukraine says are Russian soldiers have moved into Crimea, patrolling airports, smashing equipment at an air base and besieging Ukrainian military installations.
UK Foreign Secretary William Hague met Mr Yatsenyuk and laid a bouquet of flowers in Kiev's Independence Square where the killed demonstrators are being commemorated.
Mr Hague said it was urgent to get Russia and Ukraine "in direct communication with each other".
Mr Putin has defied calls from the West to pull back his troops, insisting that Russia has a right to protect its interests and those of Russian-speakers in Crimea and elsewhere in Ukraine.
His confidence is matched by the knowledge that Ukraine's 46 million people have divided loyalties.
While much of western Ukraine wants closer ties with the 28-nation European Union, its eastern and southern regions like Crimea look to Russia for support.
Faced with the Russian threat, Ukraine's new government has moved to consolidate its authority, naming new regional governors in the pro-Russia east, enlisting the support of the country's wealthy businessmen and dismissing the head of the country's navy after he declared allegiance to the pro-Russian government in Crimea.
Nato held an emergency meeting in Brussels and the US, France and Britain debated the possibility of boycotting the next G8 economic summit, to be held in June in Sochi, the host of Russia's successful Winter Olympics.
Yesterday, the White House issued a joint statement on behalf of the G7 saying they are suspending participation in the planning for the upcoming summit because Russia's advances in the Ukraine violate the "principles and values" on which the G7 and G8 operate.
So far, however, Ukraine's new government and the West have been powerless to counter Russia's tactics.
Russia has long wanted to reclaim the Crimean peninsula, part of its territory until 1954. Russia's Black Sea Fleet pays Ukraine millions annually to be stationed at the Crimean port of Sevastopol and nearly 60pc of Crimea's residents identify themselves as Russian.