The Normandy Four leaders could facilitate exchange of captives in Donbas, OSCE special representative in the Trilateral Contact Group on Ukraine Martin Sajdik said.

"It [assistance] always helps, especially if assistance would be provided in the spirit of humaneness," Sajdik told reporters in Minsk on Wednesday.

He said he was told that Russian President Vladimir Putin and Ukrainian Choice movement leader Viktor Medvedchuk had discussed the prisoner swap today. "I believe, we will see, what the numbers [regarding exchange of captives] are," Sajdik said.

"The most important thing is to show humaneness and take all possible measures to release detained persons before the end of this year. I'm actually calling for that strongly," he said.

The humanitarian subgroup continued to discuss the exchange of detained persons held by the conflicting parties in Donbas at a meeting in Minsk on Wednesday, the OSCE special envoy said.