GENEVA (AFP) - Russian Foreign Minister Sergei Lavrov on Monday harshly criticised threats of "sanctions and boycotts" over his country's role in the spiralling crisis in Ukraine, as Western powers ponder whether to kick Moscow out of the G8.

"Those who try to interpret the situation as a type of aggression and threaten sanctions and boycotts, are the same who consistently have encouraged (Ukrainians to) refuse dialogue and have ultimately polarised Ukrainian society," he told the opening of the UN Human Rights Council in Geneva.

"I call upon them to show responsibility and to set aside pure political calculations and put the interest of the Ukrainian people above all," he added.

Since Mr Putin won the Russian parliament's blessing Saturday to use force in Ukraine, including in Crimea - a strategic Black Sea peninsula with a majority ethnic Russian population - outraged Western powers have threatened to expel Russia from the Group of Eight leading industrial countries it joined with great fanfare in 1997 as it returned to global respectability after years lost in post-Soviet chaos.

UN chief Ban Ki Moon, who was scheduled to meet Mr Lavrov for a "working lunch" on Monday, also chimed in, urging Russia "to refrain from any acts and rhetoric that could further escalate the situation."

"It is critical to ensure full respect for and the preservation of Ukraine's independence, unity, sovereignty and territorial integrity," Mr Ban told reporters in Geneva.

Amid reports Monday that Russian troops were pouring into Crimea, Mr Lavrov meanwhile insisted that the Russian military presence was needed, insisting the lives of ethnic Russians in the country were in danger.

Russian President Vladimir Putin had asked the country's Federation Council for the authority "to use armed forces of Russia in the Ukraine until the normalisation of the social and political situation in that country," he said.

He insisted that ultra-nationalists control many areas of the ex-Soviet country and that the country's new leaders were attacking minority rights.

"The victors intend to make use of the fruits of their victory to attack human rights and fundamental freedoms... of minorities," he said.

"The radicals continue to control the cities" and "limit the rights of linguistic minorities."

"Violence of ultra-nationalists threatens the lives and the regional interests of Russians and the Russian-speaking population," he insisted.

"This is a question of defending our citizens and compatriots and ensuring human rights and the right to life," he said, pointing out that the "legitimate authorities of Crimea" had requested Russian assistance "to help reestablish peace in that autonomous republic."

UN chief Ban meanwhile said: "It is now of the utmost importance to restore calm and to de-escalate tensions immediately through dialogue."

Swiss President Didier Burkhalter, whose country holds the Organisation for Security and Cooperation in Europe's rotating presidency, also met Mr Lavrov in Geneva on Monday.