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President Vladimir Putin told European Commission President Jose Manuel Barroso on Monday that Russia was coordinating with the Red Cross on sending humanitarian aid to Ukraine.
"It was noted that the Russian side, in collaboration with representatives of the International Committee of the Red Cross, is sending an aid convoy to Ukraine," the Kremlin said in a statement about the telephone conversation between the two leaders.
Meanwhile, Ukraine said the humanitarian mission will be led by Red Cross and has the "blessing" of US and Russia, according to the Associated Press.
Barroso cautioned Putin against military intervention in Ukraine, the EU said.
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"President Barroso warned against any unilateral military actions in Ukraine, under any pretext, including humanitarian," it said in a statement.
Barroso also made a separate phone call to Ukrainian President Petro Poroshenko, the statement said.
In both calls, Barroso expressed the European Union's concerns about the humanitarian impact of the conflict in eastern Ukraine and called for the respect of international law.
Barroso said the EU would make an emergency decision this week on additional humanitarian support as a contribution to the U.N.-led international response plan.
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Also Monday, Ukrainian military spokesman Andriy Lysenko said Russia has massed 45,000 troops on the Ukraine border, backed by an array of heavy equipment including tanks, missile systems, warplanes and attack helicopters.
"As of 11 o'clock today, about 45,000 troops of the armed forces and internal forces of the Russian Federation are concentrated in border areas," Lysenko told a briefing.
He said they were supported by 160 tanks, 1,360 armored vehicles, 390 artillery systems, up to 150 Grad missile launchers, 192 fighter aircraft and 137 attack helicopters.
—By Reuters with CNBC. AP contributed to this report.