The leadership of the self-proclaimed Donetsk People's Republic said they do not trust Ukrainian President Petro Poroshenko's pledge to put an end to the fighting in Donbas this week.

"We don't know exactly what Poroshenko said concerning ceasefire. But we doubt that he will pull back the troops. Sloviansk was shelled with Grad launchers last night and fighting is continuing in Kramatorsk," the republic's first deputy prime minister, Andriy Purhin, told Interfax.

In his words, the mobilization of volunteers is going on in Donetsk.

"Exactly what Poroshenko meant by his statement on stopping the hostilities is a question to be addressed to Poroshenko. As for us, we continue the mobilization and the volunteers continue preparations for the defense of Donetsk," Purhin said.

The Ukrainian president earlier said that the fighting must be stopped in eastern Ukraine this week. "We must put an end to the fighting this week," Poroshenko said in Kyiv on Sunday at a meeting of the trilateral contact group for implementing the peace plan for eastern Ukraine.