This was reported by the OSCE, BBC-Ukraine informs.
The three-party contact group managed to run a video conference with representatives of the separatists, "to agree on a number of urgent measures".
During the negotiations, they promised to allow emergency services to start preparation for the bodies moving-out.
According to the latest information, 298 people became victims of the disaster.
"They (separatists) should cooperate with the appropriate Ukrainian authorities on all practical issues that arise during the rescue works and investigation", the OSCE statement says.
OSCE Chairman Didier Burkhalter offers condolences to the bereaved families.
He welcomed the readiness of the Ukrainian authorities to involve international experts into investigation. According Burkhalter, the OSCE is ready to support Ukraine in this operation by any possible mean.