The Ukrainian army made fraudulent use, on 13 May 2014, of a Mil Mi-24 helicopter displaying the colors of the UN to attack the federalists.
On 25 April, the Ukrainian government had slammed the arrest of eight military inspectors by Slavjansk federalists, asserting they were part of an OSCE delegation. The Federalists, on their part, announced that the people arrested were spies, arguing that the only mission approved by the OSCE involved 500 civilian inspectors and no military personnel.
These military inspectors (four Germans, a Czech, a Pole, a Dane and a Swede) were acting within the scope of a bilateral inspection negotiated between the Ukrainian army and the non-political administration of the OSCE. Their mandate could in no circumstances be to intervene in an internal conflict.