File Photo: Senior Ukrainian presidential aide Mykhaylo Podolyak. AFP
"An impeccable hypocrisy fair, Lavrov chairs the UNSC justifying war, mass killings, total destruction... with 'international law'," Podolyak said on Twitter in a tweet that was confirmed to AFP by a presidency official.
Russia "plainly humiliates democracy, freedom, conventions," he wrote.
Lavrov chaired a UN Security Council meeting on Monday as Russia currently holds the body's rotating presidency.
Lavrov is due to chair another meeting on Tuesday about the Middle East and give a press conference.
Ahead of Monday's meeting, Lavrov said the United Nations system was "enduring a profound crisis" and accused Western countries, particularly the United States, of being responsible.
"It's not all about Ukraine," he told reporters.
"It's about how international relations will continue to be shaped through the establishment of a sound consensus on the basis of a balance of interests or through aggressive and volatile advancement of Washington's hegemony," Lavrov added.