Putin has shown no outward sign of buckling under the weight of sanctions—the harshest yet imposed by Brussels and Washington—aimed at getting him to stop supporting pro-Russia rebels across the border in Ukraine.
The Russian Foreign Ministry described eastern Ukraine as on the verge of a "humanitarian catastrophe" and said Tuesday it would push for an international mission to help masses of civilians fleeing the fighting.
At Russia's request, the United Nations Security Council met for a briefing on the situation Tuesday night.
The Ukrainian government dismissed the initiative as cynical and said it had detected a major increase in Russia's military forces across the border.
A U.S. official confirmed there has been a buildup; a North Atlantic Treaty Organization official put the number at about 20,000 Russian troops.
Kiev and Western capitals have said they fear Russia could send troops in to support separatists under the guise of a mission to protect civilians.
Moscow denies any such plan.
But tension has been rising in recent weeks as Kiev's forces have gained ground against rebels, nearly cutting off the separatist strongholds of Donetsk and Luhansk from each other and their supply lines to Russia.
U.S. officials have accused Moscow of responding with a major increase in supplies of weapons and irregular fighters, as well as artillery and rocket attacks across the border.
Moscow denies that.
Moscow has been calling on Kiev to accept a cease-fire in a bid to save the separatists from a military defeat that would be a political setback for Putin as well.
In the last few days, Kiev's advance has appeared to slow amid heavier rebel resistance.
On Tuesday, a military spokesman said the military had retreated from Yasinuvata, a small city on the northern outskirts of Donetsk, only a day after reporting it had been taken.
The spokesman said the pullback was driven by a desire to avoid civilian casualties.
A day earlier, more than 400 Ukrainian troops who had been surrounded by rebel forces for weeks and were running out of ammunition and provisions sought temporary refuge in Russia after their comrades were unable to come to their aid.
They were returned to Ukraine on Tuesday.
Officials in Donetsk, meanwhile, reported at least two civilians were killed in shelling on the western edge of the city Tuesday.
The situation in Luhansk appeared worse, with several civilian casualties reported and water, electric and telephone service disrupted.
City officials said about half the population of 460,000 had fled.
In Geneva, the United Nations High Commissioner for Refugees said Tuesday that Ukraine had reported 117,000 people displaced within the country since the conflict began.
Russia said about 168,000 Ukrainians had crossed the border as refugees, part of an overall flow of 730,000 into its territory since the start of the conflict, UNHCR said.
Kiev has challenged Moscow's refugee figures as inflated, however.
Russia's Foreign Ministry blamed Kiev for the civilian suffering.
Its call for an international humanitarian mission seemed certain to fail amid Western opposition, but raised fears that Moscow could be planning to intervene more directly.
The U.S. and EU last week imposed another round of sanctions on Russia, affecting important economic sectors such as banking, oil and weaponry.
But Putin has shown no sign of changing tack.
On Tuesday, he said he had told the government to draw up retaliatory measures, but gave no details.
"This must be done very carefully, to support domestic producers but not harm consumers," he said during a visit to the Voronezh region.
Earlier Tuesday, Prime Minister Dmitry Medvedev said Russia would formulate its response to the European sanctions, which effectively forced the closure of Dobrolet, an airline that was flying to Crimea, the Ukrainian region that Russia annexed in March.
Russia's Vedomosti newspaper reported Tuesday that the government was considering a partial or total ban on overflights of Siberia by European airlines, which use the route to shorten trips from Europe to Asia.
Government officials declined to comment on the report, however.
In recent days, Russian regulators have banned shipments of some European fruits and vegetables and raised questions about the safety of McDonalds Corp. products in Russia, threatening to ban their sale.
Officials deny any political motivation for those moves.
Russia's central bank, meanwhile, expressed what seemed to be a rare hint of dissent late Tuesday, warning that such import restrictions would fuel already-high inflation.
Support for the Kremlin's line appears broad within Russia, however.
Local media reported that Putin and other top officials plan a special legislative session to be held in Crimea next week as a show of defiance.
A government spokeswoman declined to comment on the reports.
Source: The Wall Street Journal