• Shaun Walker in Kiev
• theguardian.com, Tuesday 26 August 2014 10.44 BST

Sources in Moscow have admitted that men captured inside Ukraine are indeed serving Russian soldiers, but said they crossed the border "by mistake". The admission comes as President Vladimir Putin is due to land in Minsk for talks with his Ukrainian counterpart on Tuesday afternoon.

Videos were released by Ukrainian authorities of interrogations of prisoners, who said they were serving Russian army officers. One said he had not been told exactly where they were going, but had an idea he was inside Ukraine. There was no immediate confirmation of the authenticity of the recordings, but the fact that Russian wire agencies ran a defence ministry admission that soldiers had indeed crossed into Ukraine suggested that the footage was genuine.

"The soldiers really did participate in a patrol of a section of the Russian-Ukrainian border, crossed it by accident on an unmarked section, and as far as we understand showed no resistance to the armed forces of Ukraine when they were detained," a source in Russia's defence ministry told the RIA Novosti agency.