A Ukrainian soldier shows a weapon allegedly belonging to Russian servicemen captured by Ukrainian forces, during a briefing for media in General Staff of Ukrainian army in Kiev, Ukraine. EPA/ROMAN PILIPEY

Kiev - Ukraine on Monday accused two captured Russian servicemen of having killed Ukrainian troops in fighting in its east and said they would be prosecuted for “terrorist acts”.

The Ukrainians seized on the capture of the two Russians, both wounded, to support their accusations of direct Russian involvement in the separatist conflict despite a ceasefire signed in February. Russia denies active military involvement.

In a video posted online by the Ukrainian interior ministry, one of the prisoners gave his name as Alexander Alexandrov. He said he had been on a spying mission in Ukraine as part of a 14-member special forces group from the central Russian town of Togliatti.

“We were discovered. I was wounded in the leg as I tried to get away ... We've been here 4-5 days,” he said.

The capture and possible prosecution of the two Russians and the potential embarrassment for Russia's Vladimir Putin come as the United States and its European Union allies press Moscow to fully implement the Minsk peace accords.

“We welcome the Ukraine government's public statements that they are being well taken care of and that the International Committee of the Red Cross... will be allowed access to them,” U.S. Assistant Secretary of State for European and Eurasian Affairs, Victoria Nuland, said in Moscow.

More than 6 100 people have been killed and Russia-West ties plunged into crisis since pro-Moscow separatists rebelled against a pro-Western leadership when it took power in Ukraine more than a year ago. Russia accuses Kiev of violating the truce.

Military spokesman Andriy Lysenko alluded to a similar previous incident and the explanation offered then by Putin.

“The leadership of the Russian Federation will have difficulty saying that these guys just got lost,” he said.

As Kiev sought to reap maximum propaganda capital from the latest incident, Ukrainian chief of staff Viktor Muzhenko told journalists that a Ukrainian soldier had carried one of the wounded Russian officers on his shoulders “while small arms and mortar fire” had continued around him.

Ukrainian Foreign Minister Pavlo Klimkin said in Brussels the prisoners had been targeted by their own side.

“Russian officers tried to kill their own people as soon as they understood they were caught by the Ukrainian military,” Klimkin told reporters.

“We are completely certain and can state that these are citizens and servicemen of the Russian Federation,” said Markiyan Lubkivsky, a senior Ukrainian state security official.

Kremlin spokesman Dmitry Peskov said: “Both we and the defence ministry have said multiple times that there are no Russian servicemen in Donbass.” Donbass is the colloquial term for Ukraine's industrialised east.

One Ukrainian soldier was killed in the fighting at Shchastya near the city of Luhansk, on Saturday, while some Ukrainian state security officials had been wounded, Kiev's state security chief Valentyn Nalivaychenko told journalists.

Nalivaychenko said the two captured Russians had personally killed Ukrainian troops.

“These (Russian) soldiers were completing their military task. They were going to kill our troops, kill our people,” military spokesman Lysenko said.

Nalivaychenko said the captured soldiers had been part of a group which had carried out acts “with a terrorist aim with guns in their hands against our citizens”.

They would be prosecuted for “terrorist activity and terrorist crimes”, he said.