"The opposition not only has failed to fulfill a single one of its obligations but is already presenting new demands all the time, following the lead of armed extremists and pogromists whose actions pose a direct threat to Ukraine's sovereignty and constitutional order,'' he told his counterparts.
Lavrov called on Berlin, Warsaw and Paris to exercise their influence with the opposition to ensure a swift fulfilment of the Feb. 21 agreement and the "restraining of rampaging hooligans''.
"It's time to stop misleading the international public opinion and pretending that the Maidan represents the interests of the Ukrainian nation,'' the statement said, referring to the Kiev square that has become the cradle of the protest movement.
Lavrov also told U.S. Secretary of State John Kerry that the peace deal signed in Ukraine had been "sharply degraded by opposition forces' inability or lack of desire'' to respect it, the ministry said. Lavrov "reminded'' Kerry that President Vladimir Putin had urged U.S. President Barack Obama during an earlier call to "use every opportunity to stop the illegal actions of radicals and return the situation to constitutional channels,'' it said.
The Moscow-backed Yanukovych on Saturday denounced events in Kiev as a coup, as the parliament voted to dismiss him and free his jailed arch-rival Yulia Tymoshenko, while protesters seized his office.
Meanwhile, leaders of mainly Russian-speaking regions of eastern Ukraine that are loyal to Yanukovych challenged the legitimacy of the national parliament and said they were taking control of their territories.
Mikhaylo Dobkin, Governor of Kharkiv region in northeast Ukraine, told regional leaders meeting in the city: "We're not preparing to break up the country. We want to preserve it.''
(Read more: Ukraine protesters seize president's office)
But a resolution adopted at the meeting said: "The decisions taken by the Ukrainian parliament in such circumstances cause doubts about their ... legitimacy and legality.''
It added: "The central state organs are paralyzed. Until the constitutional order and lawfulness are restored ... we have decided to take responsibility for safeguarding the constitutional order, legality, citizens' rights and their security on our territories.''
One speaker urged the creation of civilian patrols to restore order. Another said those gathered should fear reprisals if anti-Yanukovych protesters in Kiev seize power in the whole of the country.
With people at the meeting chanting "Russia! Russia!'', the atmosphere contrasted with the mood in the capital Kiev where protesters want the Moscow-backed Yanukovych to resign.
Yanukovych said he had no intention of quitting or leaving Ukraine and declared all moves taken by parliament on Saturday to be illegal and amounting to a "coup d'etat'', Russian news agency Interfax reported, citing a television interview.
(Read more: The quiet billionaires shaping Ukraine's future)
A day after Yanukovych signed an agreement with the opposition to relinquish some of his powers, his opponents were in control of the presidential administration and the Interior Ministry responsible for the police turned its back on him.
The regions represented at the meeting—Kharkiv, Donetsk, Dnipropetrovsk, Lugansk and Crimea—have a population of 14.4 million. Most are important industrial centres and Russia's Black Sea fleet is based in the Crimean port of Sevastopol.
Talk of a split
Many politicians have warned of a looming partition in Ukraine, which broke peacefully from the Soviet Union in 1991, since people took to the streets late last year to protest against Yanukovych for spurning political and trade deals with the European Union. Western Ukraine is broadly pro-EU.
Some Ukrainians are also worried by calls in Crimea for the region to again become Russian territory, nearly six decades after Kremlin leader Nikita Khrushchev—who was a Ukrainian—redrew internal Soviet boundaries to make a gift of the peninsula to Ukraine.