A Ukrainian soldier stands guard at a checkpoint outside the city of Slaviansk
A Ukrainian soldier stands guard at a checkpoint outside the city of Slaviansk April 27, 2014. The leader of separatist rebels holding a group of international observers in the Ukrainian city of Slaviansk said he was scheduled on Sunday to meet a delegation of mediators who were on their way to negotiate the observers' release. REUTERS/Gleb Garanich (UKRAINE - Tags: POLITICS CIVIL UNREST MILITARY)
A Ukrainian soldier patrols through a field at a check point near Slaviansk
A Ukrainian soldier patrols through a field at a check point near Slaviansk, in eastern Ukraine April 27, 2014. The de facto mayor of the Ukrainian city of Slaviansk said on Sunday mediators from the Organisation for Security and Cooperation in Europe who are seeking the release of a group of detained observers had arrived in the city. (UKRAINE - Tags: POLITICS CIVIL UNREST MILITARY)
Ponomaryov and international observers take part in a meeting with journalists in the eastern Ukrainian city of Slaviansk
Vyacheslav Ponomaryov (4th R), separatist de facto mayor of Slaviansk, and international observers take part in a meeting with journalists in the eastern Ukrainian city of Slaviansk April 27, 2014. The leader of the international observers detained by pro-Russian separatists in the east Ukrainian city of Slaviansk said on Sunday all the group were in good health, but they were anxious to be allowed to go home soon. REUTERS/Gleb Garanich (UKRAINE - Tags: POLITICS CIVIL UNREST TPX IMAGES OF THE DAY)
A Ukrainian soldier holds a rifle as he stands on an armoured personnel carrier at a check point near Slaviansk
A Ukrainian soldier holds a rifle as he stands on an armoured personnel carrier at a check point near Slaviansk, in eastern Ukraine April 27, 2014. The de facto mayor of the Ukrainian city of Slaviansk said on Sunday mediators from the Organisation for Security and Cooperation in Europe who are seeking the release of a group of detained observers had arrived in the city. (UKRAINE - Tags: POLITICS CIVIL UNREST MILITARY)
A Ukrainian soldier eats his meal in a field at a check point near Slaviansk
A Ukrainian soldier eats his meal in a field at a check point near Slaviansk, in eastern Ukraine April 27, 2014. The de facto mayor of the Ukrainian city of Slaviansk said on Sunday mediators from the Organisation for Security and Cooperation in Europe who are seeking the release of a group of detained observers had arrived in the city. REUTERS/Marko Djurica (UKRAINE - Tags: POLITICS CIVIL UNREST MILITARY)
A Ukrainian soldier adjusts a stop sign at a check point near Slaviansk
A Ukrainian soldier adjusts a stop sign at a check point near Slaviansk, in eastern Ukraine April 27, 2014. The de facto mayor of the Ukrainian city of Slaviansk said on Sunday mediators from the Organisation for Security and Cooperation in Europe who are seeking the release of a group of detained observers had arrived in the city. REUTERS/Marko Djurica (UKRAINE - Tags: POLITICS CIVIL UNREST MILITARY)
A Ukrainian soldier holds a weapon as he stands on an armoured personnel carrier at a check point near Slaviansk
A Ukrainian soldier holds a weapon as he stands on an armoured personnel carrier at a check point near Slaviansk, in eastern Ukraine April 27, 2014. The de facto mayor of the Ukrainian city of Slaviansk said on Sunday mediators from the Organisation for Security and Cooperation in Europe who are seeking the release of a group of detained observers had arrived in the city. REUTERS/Marko Djurica (UKRAINE - Tags: POLITICS CIVIL UNREST MILITARY)
A Ukrainian soldier walks near armoured personnel carriers at a check point near Slaviansk
A Ukrainian soldier walks near armoured personnel carriers at a check point near Slaviansk, in eastern Ukraine April 27, 2014. The de facto mayor of the Ukrainian city of Slaviansk said on Sunday mediators from the Organisation for Security and Cooperation in Europe who are seeking the release of a group of detained observers had arrived in the city. REUTERS/Marko Djurica (UKRAINE - Tags: POLITICS CIVIL UNREST MILITARY)
Ukrainian soldiers check on vehicles at a check point near Slaviansk
Ukrainian soldiers check on vehicles at a check point near Slaviansk, in eastern Ukraine April 27, 2014. The de facto mayor of the Ukrainian city of Slaviansk said on Sunday mediators from the Organisation for Security and Cooperation in Europe who are seeking the release of a group of detained observers had arrived in the city. REUTERS/Marko Djurica (UKRAINE - Tags: POLITICS CIVIL UNREST MILITARY)
A Ukrainian soldier cleans his rifle as he stands on an armoured personnel carrier at a check point near Slaviansk
A Ukrainian soldier cleans his rifle as he stands on an armoured personnel carrier at a check point near Slaviansk, in eastern Ukraine April 27, 2014. The de facto mayor of the Ukrainian city of Slaviansk said on Sunday mediators from the Organisation for Security and Cooperation in Europe who are seeking the release of a group of detained observers had arrived in the city. REUTERS/Marko Djurica (UKRAINE - Tags: POLITICS CIVIL UNREST MILITARY TPX IMAGES OF THE DAY)