A pro-Russia activist hangs a flag of the so-called "People's Republic of Donetsk" on the regional administration building seized by separatists as armed men in military fatigues guard the premises in the eastern Ukrainian city of Slavyansk on April 21, 2014. US Vice President Joe Biden will begin a two-day visit to Ukraine, hours after a fragile Easter truce was shattered and pro-Kremlin rebels in the country's east appealed for help from Russian "peacekeepers". AFP PHOTO / GENYA SAVILOV        (Photo credit should read GENYA SAVILOV/AFP/Getty Images)