NATO has warned Moscow that any attempt by Russian-backed separatists to take more territory in eastern Ukraine would be "unacceptable."
NATO said in a statement on August 19 that its 28 member states had discussed the recent escalation in violence in Ukraine and added that "Russia has a special responsibility to find a political solution" to the crisis.
It called on all parties to "de-escalate tensions and exercise restraint."
NATO said any attempt by the rebels to move further into Ukraine would be "unacceptable to the international community."
Fighting between government forces and the separatist forces around the southern port city of Mariupol in recent days has led to several people being killed.
NATO also called on all sides to ensure that monitors from the Organization for Security and Cooperation in Europe (OSCE) can perform their jobs "safely and without restrictions."
More than 6,400 people have been killed in eastern Ukraine since March 2014.
Based on reporting by Reuters and dpa