Speaking at a briefing in Moscow right now, Russian President Vladimir Putin stated that Russia is “seriously concerned” regarding the possibility of Ukraine acquiring nuclear weapons.
Putin cited recent remarks made by Ukrainian President Volodymyr Zelenskiy on the subject of Ukraine having given up its nuclear arsenal were "targeted at Russia."
Asked whether Russian troops would be deployed to the newly-recognized separatist republics and even beyond, Putin did not give a direct answer, saying that it would depend on the situation on the ground.