MOSCOW — The two sides in what is developing into an East-West clash over Ukraine hardened their positions on Wednesday, with Russian officials denouncing what they called a coup by right-wing extremists, even as the United States and Europe threatened to impose sanctions on those responsible for the violence that has erupted in the capital, Kiev, and spread to other cities.

The starkly divergent reactions underscored the deepening confrontation between Russia and the West over Ukraine’s fate, with each side accusing the other of interference and disputing even the facts of what was happening.

Expressing alarm at the escalating death toll, Chancellor Angela Merkel of Germany and President François Hollande of France blamed the security forces of President Viktor F. Yanukovych and made it clear that they supported a political transition that would allow Ukrainians to elect a new government. After meeting with Mr. Hollande in Paris, Ms. Merkel said the convulsion of violence resulted from a “deliberate delaying tactic” by Mr. Yanukovych to avoid a compromise and preserve his place in power.

Russia, by contrast, vowed to use all its influence to support Ukraine’s government and joined Mr. Yanukovych in accusing his opponents of trying to seize power in what amounted to a coup. In one of its most pointed statements since the political crisis in Ukraine began, the Russian Foreign Affairs Ministry even evoked the Brown Revolution that brought the Nazis to power in Germany in 1933, blaming “criminal activities of radical opposition forces” for causing the bloodshed and denouncing European countries for failing to acknowledge that.