The Organization for Security and Cooperation in Europe, monitoring a fragile cease-fire in eastern Ukraine, has called on Ukraine and Russian-backed separatists to do more to investigate violations of the agreement.
Alexander Hug, deputy director of the OSCE monitoring mission in Ukraine, told Reuters that both sides often failed to investigate and take action on cease-fire violations, such as the discovery of unauthorized weapons, the downing of drones and attacks on OSCE personnel.
"Both sides are equally guilty, and increase the feeling that... there is no political cost for non-compliance," Hug said in an interview on Tuesday.
Hug said the cease-fire had resulted in the withdrawal of many weapons from the region and far fewer deaths than a year ago, but the process remained unpredictable and flawed.
The number of cease-fire violations had dropped in recent days, Hug said, but he warned that the situation was "very unstable" and unpredictable.
"It is now time - rather than trying to find new ways to regulate the conflict - that those remedies that have been agreed should be implemented in full," he said.
Only then, he said, would it become clear which side was "undertaking actual, real measures to stop the fighting".
European Union officials agreed on Tuesday to extend until the end of January a host of energy, financial and defense sanctions imposed on Russia over the conflict in Ukraine.
EU politicians including German Foreign Minister Frank-Walter Steinmeier are urging a softer stance towards Russia, a key trade partner and energy provider.
German Chancellor Angela Merkel continues to insist sanctions against Russia can only be unwound once Moscow fully implements the Minsk peace deal for eastern Ukraine.