Russia has sentenced an Australian man to 13 years in a maximum-security prison for fighting alongside Ukrainian forces, state prosecutors in the Russian-controlled parts of eastern Ukraine said Friday.

Russia and Ukraine agreed to exchange 1,000 prisoners of war each during peace talks held in Istanbul on Friday, in what would be the biggest prisoner swap of the conflict. The negotiations, which lasted less than two hours and were mediated by Turkey,

But the two sides failed to broker a temporary cease-fire or a meeting between their two leaders, a sign of how far apart they remain on ending the conflict.