Ukraine conflict: Russian 'outrage' at Sloviansk attack
21 April 2014 Last updated at 17:19 BST
US Vice President Joe Biden has arrived in Ukraine, as a war of words is growing between Moscow and Kiev.
Russian Foreign Minister Sergei Lavrov has accused the Ukrainian authorities of breaking a deal reached last week and failing to rein in the ultra-nationalist group the Right Sector.
Russia has accused the group of carrying out a shooting in Sloviansk on Sunday.
David Stern reports.