The leaders of France, Germany, Russia and Ukraine discussed aspects of socioeconomic development of Donbas at negotiations in the Normandy Quartet format in Paris on Friday, Ukrainian President Petro Poroshenko said.

"The conversation concerned the unacceptability of the use of force against and the shooting at our experts dispatched under the Ukrainian government's instructions to restore water and energy supply systems and railways. We consider this categorically unacceptable, and statements on this account were made," Poroshenko told journalists following negotiations between the Normandy Quartet leaders in Paris on Friday.

The Ukrainian leader emphasized that the negotiations had been difficult.

"But I believe the results of our joint and energetic actions with our European partners brought about certain results," he said.