Members of the Ukrainian armed forces gather on armoured vehicles on the roadside near the village of Vidrodzhennya outside Artemivsk, Donetsk region, Ukraine, June 9, 2015. REUTERS/Oleksandr Klymenko TPX IMAGES OF THE DAY

Members of the Ukrainian armed forces take their positions near the town of Maryinka, eastern Ukraine, June 9, 2015. Eight Ukrainian servicemen have been killed - seven of them in a single land mine blast - in the past 24 hours in eastern Ukraine where government forces are battling pro-Russian separatists, Kiev's military spokesman said on Tuesday. REUTERS/Gleb Garanich TPX IMAGES OF THE DAY

Members of the Ukrainian armed forces are seen at their positions near the town of Maryinka, eastern Ukraine, June 9, 2015. Eight Ukrainian servicemen have been killed - seven of them in a single land mine blast - in the past 24 hours in eastern Ukraine where government forces are battling pro-Russian separatists, Kiev's military spokesman said on Tuesday. REUTERS/Gleb Garanich 

Members of the Ukrainian armed forces shake hands at their positions in the town of Maryinka, eastern Ukraine, June 9, 2015. Eight Ukrainian servicemen have been killed - seven of them in a single land mine blast - in the past 24 hours in eastern Ukraine where government forces are battling pro-Russian separatists, Kiev's military spokesman said on Tuesday. REUTERS/Gleb Garanich 

Members of the Ukrainian armed forces sit on an armoured vehicle along a roadside near the village of Vidrodzhennya outside Artemivsk, Donetsk region, Ukraine, June 9, 2015. REUTERS/Oleksandr Klymenko 

Members of the Right Sector's Ukrainian Volunteer Corps watch television as they rest at the Butovka coal mine near Donetsk, Ukraine, June 7, 2015. Picture taken June 7, 2015. REUTERS/Oleksandr Klymenko 

Members of the Right Sector's Ukrainian Volunteer Corps prepare ammunition at the Butovka coal mine near Donetsk, Ukraine, June 7, 2015. Picture taken June 7, 2015. REUTERS/Oleksandr Klymenko 

Members of the Right Sector's Ukrainian Volunteer Corps rest in the Butovka coal mine near Donetsk, Ukraine, June 7, 2015. Picture taken June 7, 2015. REUTERS/Oleksandr Klymenko 

Ukrainian servicemen rest at their positions located in the village of Shirokino near Mariupol, Ukraine, June 7, 2015. REUTERS/Maksim Levin 

A Ukrainian serviceman stands guard at positions located in the village of Shirokino near Mariupol, Ukraine, June 6, 2015. Picture taken June 6, 2015. REUTERS/Maksim Levin 

A member of the Ukrainian armed forces gets down a trench located near the town of Horlivka, north of Donetsk, Ukraine, June 6, 2015. REUTERS/Oleksandr Klymenko 

Members of the Ukrainian armed forces prepare a weapon at their position located near the town of Horlivka, north of Donetsk, Ukraine, June 6, 2015. REUTERS/Oleksandr Klymenko 

Members of the Ukrainian armed forces look out from a blindage at their positions in the village of Pisky (Pesky) near the local airport, north-west of Donetsk, Ukraine, June 5, 2015. REUTERS/Oleksandr Klymenko TPX IMAGES OF THE DAY

A member of the Ukrainian armed forces is seen in the town of Maryinka, eastern Ukraine, June 5, 2015. Ukraine's president told his military on Thursday to prepare for a possible "full-scale invasion" by Russia all along their joint border, a day after the worst fighting with Russian-backed separatists in months. REUTERS/Gleb Garanich 

A Ukrainian serviceman holds a mortar round together with a rose at his position in the town of Maryinka, eastern Ukraine, June 5, 2015. Ukraine's president told his military on Thursday to prepare for a possible "full-scale invasion" by Russia all along their joint border, a day after the worst fighting with Russian-backed separatists in months. REUTERS/Gleb Garanich TPX IMAGES OF THE DAY

Members of the Ukrainian armed forces walk at their positions located in the village of Pisky (Pesky) near the local airport, outside Donetsk, Ukraine, June 5, 2015. REUTERS/Oleksandr Klymenko 

A tattered Ukrainian national flag flutters in the wind at a position held by the Ukrainian armed forces near the town of Maryinka, eastern Ukraine, June 5, 2015. Ukraine's president told his military on Thursday to prepare for a possible "full-scale invasion" by Russia all along their joint border, a day after the worst fighting with Russian-backed separatists in months. REUTERS/Gleb Garanich 

A member of the Ukrainian armed forces is seen in the town of Maryinka, eastern Ukraine, June 5, 2015. Ukraine's president told his military on Thursday to prepare for a possible "full-scale invasion" by Russia all along their joint border, a day after the worst fighting with Russian-backed separatists in months. REUTERS/Gleb Garanich 

A local resident walks along the street in the town of Maryinka, eastern Ukraine, June 5, 2015. Ukraine's president told his military on Thursday to prepare for a possible "full-scale invasion" by Russia all along their joint border, a day after the worst fighting with Russian-backed separatists in months. REUTERS/Gleb Garanich 

A Ukrainian serviceman digs trenches at his position in Avdeyevka near Donetsk, Ukraine, June 4, 2015. Ukraine's president Petro Poroshenko told his military on Thursday to be prepared for the possibility of a "full-scale invasion" by Russia across the entire length of the joint border, a day after the worst fighting with Russian-backed separatists in months. REUTERS/Oleksandr Klymenko 

A member of the Ukrainian armed forces is seen at his position in the town of Maryinka, eastern Ukraine, June 5, 2015. Ukraine's president told his military on Thursday to prepare for a possible "full-scale invasion" by Russia all along their joint border, a day after the worst fighting with Russian-backed separatists in months. REUTERS/Gleb Garanich TPX IMAGES OF THE DAY

A member of the Ukrainian armed forces is seen near the town of Maryinka, eastern Ukraine, June 5, 2015. Ukraine's president told his military on Thursday to prepare for a possible "full-scale invasion" by Russia all along their joint border, a day after the worst fighting with Russian-backed separatists in months. REUTERS/Gleb Garanich 

Members of the Ukrainian armed forces patrol an area in the town of Maryinka, eastern Ukraine, June 5, 2015. Ukraine's president told his military on Thursday to prepare for a possible "full-scale invasion" by Russia all along their joint border, a day after the worst fighting with Russian-backed separatists in months. REUTERS/Gleb Garanich 

A boy sits on a swing near his building, which was damaged during fighting between the Ukrainian army and pro-Russian separatists, as an armoured personnel carrier (APC) of the Ukrainian armed forces is seen nearby in Avdeyevka near Donetsk, eastern Ukraine, June 7, 2015. Group of Seven (G7) leaders vowed at a summit in the Bavarian Alps on Sunday to keep sanctions against Russia in place until President Vladimir Putin and Moscow-backed separatists fully implement the terms of a peace deal for Ukraine. REUTERS/Gleb Garanich

A member of the Right Sector's Ukrainian Volunteer Corps fires a weapon from his position during clashes with pro-Russian separatists at the Butovka coal mine near Donetsk, Ukraine, June 7, 2015. Picture taken June 7, 2015. REUTERS/Oleksandr Klymenko