Representatives of the self-proclaimed Donetsk and Luhansk people's republics have shown an interest in peace talks, Ukrainian President Petro Poroshenko said.

"We have received a confirmation that they demonstrated an interest in participating [in the negotiations] practically half an hour ago," Poroshenko said at a session of the Parliamentary Assembly of the Council of Europe (PACE) in Strasbourg.

"If this [option] is rejected tomorrow we will make a very important decision," the chief of state said declining to specify what decision that might be.

Illegal armed units continued hostilities after Ukraine had proclaimed the ceasefire, he said. Ukrainian workers were repairing railroad tracks and other utilities under fire in order to normalize supplies to the local population, Poroshenko said.

Kyiv did its best to achieve peace by presenting a peace plan and drawing up amendments to the constitution and an amnesty bill, the president stressed.

"If the hands we stretch out in a gesture of peace hang in the air it will be hard to keep our position for long," Poroshenko said in answer to the question whether gunfire would resume in the case the militia refused to lay down arms.

As reported, Poroshenko ordered law enforcement units in his trip to Donbas on June 20 to cease fire so that the militia could lay down arms. The order was given to all units of the Armed Forces, the National Guard and the State Border Service for the period of one week, from June 20 to 27.

On the same day the Ukrainian president publicized his peace plan incorporating 15 steps, among them disarmament, liberation of occupied buildings and hostages and power decentralization through constitutional amendments.