Tanks are seen on a freight train shortly after its arrival at a railway station, with people walking in the foreground, in the Russian southern town of Matveev Kurgan, near the Russian-Ukrainian border in Rostov region, Russia, May 26, 2015. Picture taken with a mobile phone. REUTERS/Maria Tsvetkova 

A tank drives along a street of the Russian southern town of Matveev Kurgan, near the Russian-Ukrainian border in Rostov region, Russia, May 26, 2015. The convoy of nine tanks, which were delivered by train the day before, drove along streets of the town on Tuesday, according to a Reuters journalist. Picture taken with a mobile phone. REUTERS/Maria Tsvetkova 

A picture shows a military convoy on the road side of the Russian southern town of Matveev Kurgan, near the Russian-Ukrainian border in Rostov region, Russia, May 26, 2015. Picture taken with a mobile phone. REUTERS/Maria Tsvetkova 

A goat walks in a field during military exercises at the Russian military training ground 'Kuzminsky' near the Russian-Ukrainian border in the Rostov region, Russia, May 26, 2015. Picture taken with a mobile phone. REUTERS/Maria Tsvetkova 

Multiple launch rocket systems and military trucks are seen on freight train platforms in the Russian southern town of Matveev Kurgan ,near the Russian-Ukrainian border in Rostov region, Russia, May 23, 2015. A train with about 20 multiple launch rocket systems and dozens of military trucks, accompanied by Russian servicemen, arrived on May 23 in Matveev Kurgan, according to a Reuters journalist. REUTERS/Stringer 

Multiple launch rocket systems and military trucks are seen on freight train flatcars in the Russian southern town of Matveev Kurgan, near the Russian-Ukrainian border in Rostov region, Russia, May 25, 2015. The sign reads, "Dangerous! Railway is not a place for games!" REUTERS/Maria Tsvetkova 

A woman with a boy looks at a tank as it drives through the settlement Khutor Chkalova on its way to the Russian military training ground 'Kuzminsky' near the Russian-Ukrainian border in the Rostov region, Russia, May 26, 2015. Picture taken with a mobile phone. REUTERS/Maria Tsvetkova 

Vehicles are parked outside a camp at the Russian military training ground 'Kuzminsky' near the Russian-Ukrainian border in the Rostov region, Russia, May 23, 2015. REUTERS/Stringer 

Trucks transport tanks along a road near the Russian southern town of Matveev Kurgan, near the Russian-Ukrainian border in Rostov region, Russia, May 26, 2015. Picture taken with a mobile phone. REUTERS/Maria Tsvetkova 

A military convoy is seen parked near a field outside the Russian southern town of Matveev Kurgan, near the Russian-Ukrainian border in Rostov region, Russia, May 26, 2015. Picture taken with a mobile phone. REUTERS/Maria Tsvetkova 

A truck transports an armored military vehicle near the Russian southern town of Matveev Kurgan, near the Russian-Ukrainian border in Rostov region, Russia, May 26, 2015. Picture taken with a mobile phone. REUTERS/Maria Tsvetkova 

A truck and a multiple launch rocket system travel at the Kuzminsky military training ground near the Russian southern village of Chkalovo in the Rostov region, Russia, May 24, 2015. The convoy of dozens military vehicles including Uragan multiple rocket launchers, military trucks without license plates and few armoured personnel carriers (APC) crossed the southern Russian town of Matveyev Kurgan on May 24 and turned to the fields from the road near the border with Ukraine, according to a Reuters journalist. REUTERS/Stringer 

Tanks drive along a street of the Russian southern town of Matveev Kurgan, near the Russian-Ukrainian border in Rostov region, Russia, May 26, 2015. The convoy of nine tanks, which were delivered by train the day before, drove along streets of the town on Tuesday, according to a Reuters journalist. Picture taken with a mobile phone. REUTERS/Maria Tsvetkova