Riot police stand guard in front of the regional administration building in Luhansk
Riot police stand guard in front of the regional administration building in Luhansk, eastern Ukraine, April 28, 2014. Several dozen pro-Russian and pro-Ukranian activists argued and exchanged threats as they gathered at the same place in the city. REUTERS/Vasily Fedosenko (UKRAINE - Tags: POLITICS CIVIL UNREST TPX IMAGES OF THE DAY)
Pro-Russian protesters return riot shields after a pro-Ukraine rally in the eastern city of Donetsk
Pro-Russian protesters return riot shields after a pro-Ukraine rally in the eastern city of Donetsk April 28, 2014. Several people were wounded when what appeared to be stun grenades exploded during a rally in support of Ukrainian unity in the eastern, separatist-held city of Donetsk on Monday, a Reuters reporter said. REUTERS/Marko Djurica (UKRAINE - Tags: POLITICS CIVIL UNREST)
Riot police are seen at a police station in Luhansk
Riot police are seen at a police station in Luhansk, eastern Ukraine, April 28, 2014. Several dozen pro-Russian and pro-Ukranian activists argued and exchanged threats as they gathered at the same place in the city. REUTERS/Vasily Fedosenko (UKRAINE - Tags: POLITICS CIVIL UNREST)
Mastercard to stop services to sanctioned Russian banks
UKRAINE-CRISIS/SANCTIONS-MASTERCARD:Mastercard to stop services to sanctioned Russian banks
An Ukranian riot officer looks from a bus during a pro-Ukraine rally in the eastern city of Donetsk
An Ukranian riot officer looks from a bus during a pro-Ukraine rally in the eastern city of Donetsk April 28, 2014. Several people were wounded when what appeared to be stun grenades exploded during a rally in support of Ukrainian unity in the eastern, separatist-held city of Donetsk on Monday, a Reuters reporter said. REUTERS/Marko Djurica (UKRAINE - Tags: POLITICS CIVIL UNREST)
Pro-Ukranian protesters light flares during a rally in the eastern city of Donetsk
Pro-Ukranian protesters light flares during a rally in the eastern city of Donetsk April 28, 2014. Several people were wounded when what appeared to be stun grenades exploded during a rally in support of Ukrainian unity in the eastern, separatist-held city of Donetsk on Monday, a Reuters reporter said. REUTERS/Marko Djurica (UKRAINE - Tags: POLITICS CIVIL UNREST)
Pro-Ukranian activists stand in front of a police station during a rally in Luhansk
Pro-Ukranian activists stand in front of a police station during a rally in Luhansk, eastern Ukraine, April 28, 2014. Several dozen pro-Russian and pro-Ukranian activists argued and exchanged threats as they gathered at the same place in the city. REUTERS/Vasily Fedosenko (UKRAINE - Tags: POLITICS CIVIL UNREST)
Pro-Russian protesters march with riot police shields during a pro-Ukraine rally in the eastern city of Donetsk
Pro-Russian protesters march with riot police shields during a pro-Ukraine rally in the eastern city of Donetsk April 28, 2014. Several people were wounded when what appeared to be stun grenades exploded during a rally in support of Ukrainian unity in the eastern, separatist-held city of Donetsk on Monday, a Reuters reporter said. REUTERS/Marko Djurica (UKRAINE - Tags: POLITICS CIVIL UNREST)
Pro-Ukranian protesters shout slogans during a rally in the eastern city of Donetsk
Pro-Ukranian protesters shout slogans during a rally in the eastern city of Donetsk April 28, 2014. Several people were wounded when what appeared to be stun grenades exploded during a rally in support of Ukrainian unity in the eastern, separatist-held city of Donetsk on Monday, a Reuters reporter said. REUTERS/Marko Djurica (UKRAINE - Tags: POLITICS CIVIL UNREST)
Pro-Ukranian activists walk in Luhansk
Pro-Ukranian activists walk in Luhansk, eastern Ukraine, April 28, 2014. Several dozen pro-Russian and pro-Ukranian activists argued and exchanged threats as they gathered at the same place in the city. REUTERS/Vasily Fedosenko (UKRAINE - Tags: POLITICS CIVIL UNREST)