Ukrainian President Petro Poroshenko has offered condolences to the families and friends of the OSCE SMM (Organization for Security and Co-operation in Europe's Special Monitoring Mission to Ukraine) employee killed in a blast that hit a patrol car carrying the mission's observers when it ran over a landmine in that part of the Luhansk region not controlled by Kyiv; Poroshenko has urged holding an investigation of the crime.

"I express condolences to the families and friends of the killed representative of the OSCE Special Monitoring Mission. And I wish those injured to recover soon. I have given appropriate tasks: Ukrainian medics are ready to provide all necessary aid, if needed," Poroshenko said on his Facebook page on Sunday.

Poroshenko emphasized that the crime must be investigated and those guilty punished. "I have ordered the foreign minister [Pavlo Klimkin] to be in constant coordination with the OSCE," Poroshenko added.

"The Ukrainian side condemns all forms in which the work of the OSCE SMM is constantly being obstructed by militants. The mission's security and freedom of action must be guaranteed," Poroshenko said.