Kyiv is negotiating the soonest release of 25 Ukrainian hostages, advisor to the Ukrainian Security Service head Yuriy Tandyt said.

"We are ready for various compromises; a 25 for 50 formula is currently being discussed," Tandyt said in an interview with the ICTV Channel aired on Sunday evening.

Kyiv is doing the utmost for the release of prisoners, he said.

"We will do everything for the soonest release of our 25 hostages," he added.