A source from the group told Interfax, Censor.NET reports.
"So far it was not possible to reach an agreement and set the date for the start of the release of detained persons," the source said.
The group representative also said the talks are quite tense.
"The contradictions of the sides are too strong, so no chance to speak of efficient process so far," the source told the agency.
Russia should withdraw thousands of its military from Ukraine and stop supporting militants, - Stoltenberg(0)
Russian fighter Ageev, captured by Ukrainian army on June 24, "left military service" last year, - Russian MoD(0)