A pro-Russian armed activist guards barricades outside the security service (SBU) regional building seized by the separatists in the eastern Ukrainian city of Slavyansk on April 23, 2014. Pro-Kremlin rebels in Ukraine braced Wednesday for a renewed military offensive by Kiev as US troops headed to region in a show of force after Washington again warned Moscow over the escalating crisis. AFP PHOTO/GENYA SAVILOV        (Photo credit should read GENYA SAVILOV/AFP via Getty Images)