As reported Censor.NET referring to Interfax-Ukraine, this was announced on Monday by the US State Department spokesman John Kirby.
He expressed utter concern by the sharp increase of attacks by the combined forces of Russia and militants across the cease-fire line in eastern Ukraine, noting that over the past weekend, attacks in particular occurred to the north and east of Mariupol.
According to him, there can be no mistake as to those responsible, Russia and separatists' attacks being reminiscent of the last August escalation of the conflict.
According to Kirby, the OSCE monitors confirm the majority of attacks were carried out by the combined forces of Russia and militants.
Kirby also called for immediate cease-fire in the east of Ukraine and full compliance with the Minsk agreements.