(Adds Medvedev quotes)
MOSCOW, Feb 24 (Reuters) - Russia's prime minister voiced grave doubts on Monday over the legitimacy of the authorities in Ukraine after President Viktor Yanukovich's ouster, criticising Western states for recognising officials he said came to power in an "armed mutiny".
In some of Russia's strongest statements condemning the toppling of the Moscow-backed leader, Prime Minister Dmitry Medvedev made clear he was not yet ready to engage with the former opposition figure appointed acting leader by parliament.
"We do not understand what is going on there. There is a real threat to our interests and to the lives of our citizens," Medvedev was quoted as telling Russian news agencies, explaining why Moscow had recalled its Kiev ambassador on Sunday.
"Strictly speaking there is no one to talk to there. There are big doubts about the legitimacy of a whole series of organs of power that are now functioning there," he said.
Medvedev described some of the opposition activists involved in the street protests that led to Yanukovich's demise as "men in black masks with Kalashnikovs who are carving up Kiev," the reports said.
"It will be hard for us to work with such a government," state-run RIA quoted him as saying. "Some of our foreign partners think differently ... it seems to me it is an aberration to call legitimate what is essentially the result of an armed mutiny," he added. (Reporting by Alissa de Carbonnel; Editing by Steve Gutterman)