US said that a false flag operation would give Russia the pretext to invade Ukraine by provoking shock and outrage. The Biden administration sought to undermine its emotional power and stop the Kremlin from manufacturing a casus belli, or justification for war.

NATO and allied countries were monitoring and assessing the situation very closely, according to the official, and continue to take all the necessary measures.Lviv is in the far west of Ukraine. Many countries have moved diplomats there from Kyiv further in the east.

Russia's foreign ministry spokeswoman, Maria Zakharova, questioned if the United States had passed on the information about possible attacks to Russia."And if not, how is one to understand all of this?" Zakharova said.

Russia Ukraine conflict highlights: Tensions along the Ukraine border heightened on Friday. Russian President Vladimir Putin accused Ukraine of committing human rights violations against Russian minorities. Meanwhile, separatist leaders in the breakaway Ukrainian regions of Donetsk and Luhansk ordered large-scale civilian evacuations, fuelling fresh fears from Western countries that Russia would use this as a pretext to invade Ukraine. US Vice-President Kamala Harris, speaking at the Munich Security Conference, said Russia must show it is serious about diplomacy, while French president Emmanuel Macron has called for a cessation of hostilities. A large explosion was reported near the rebel HQ in Donetsk city.