“Steps are being taken – above all by those who seized power in Kiev – that not only do not fulfil, but that crudely violate, the Geneva agreement,” he said.
Mr Lavrov also told a news conference that a deadly gun battle early on Sunday near the Ukrainian city of Slaviansk, which is controlled by pro- Russian separatists, was a crime and showed that Kiev did not want to control “extremists”.
He said: “The authorities are doing nothing, not even lifting a finger, to address the causes behind this deep internal crisis in Ukraine.”
At least three people were killed in the shootout, shaking an already fragile accord reached last Thursday between Russia, Ukraine, the United States and the European Union.
The agreement called for an immediate end to violence in Ukraine, where Western powers believe Russia is encouraging a separatist movement, which Moscow denies.
The accord also called for illegal armed groups to go home in a process to be overseen by the EU’s security arm, the Organisation for Security and Co-operation in Europe (OSCE).
However, separatists have shown little sign of quitting public buildings in the largely Russian-speaking eastern Ukraine.
They have declared an independent “People’s Republic of Donetsk” in the east’s biggest province and appointed themselves to official posts in towns and cities, setting up checkpoints and flying Russian flags over government buildings.
Ukraine announced an “anti-terrorist” operation to retake the territory last week, but that modest effort largely collapsed in disarray when a column of paratroops surrendered rifle parts and some armoured vehicles to a separatist crowd.
Kiev has declared an “Easter truce”, though it is far from clear whether it could muster any real force if it tried.
The army is ill-equipped, untested and untrained for domestic operations, while the government in Kiev doubts the loyalty of the police.
The US has demanded that Russia use what power Washington believes it has over the separatists – though Moscow insists it has none – to force them to leave the buildings. It has also warned of stronger economic sanctions than those already imposed if Moscow fails to uphold the Geneva deal.
However, Mr Lavrov hit back: “Before giving us ultimatums, demanding that we fulfil demands within two or three days with the threat of sanctions, we would urgently call on our American partners to fully accept responsibility for those who they brought to power.”
He added that attempts to isolate Russia would fail because it was “a big, independent power that knows what it wants”.
Mr Lavrov spoke as American vice-president Joe Biden arrived in Kiev yesterday for a two-day visit, in an effort to demonstrate his country’s commitment to Ukraine.
He has meetings today with the acting Ukrainian prime minister and president.
Elsewhere, three foreign journalists were temporarily held by pro-Russia insurgents in eastern Ukraine.
One Belarussian and two Italian journalists were stopped by gunmen in the city of Slovyansk, which has been occupied by pro-Russia forces for more than a week.
Slovyansk is one of many cities in Ukraine’s eastern region where insurgents are demanding greater ties with Russia.
Dmitry Galko said that he and two Italian colleagues were freed later after a document check.