MOSCOW — International monitors tracking cease-fire violations in eastern Ukraine reported Friday that they had encountered four people wearing military uniforms with Russian insignia in a town about 25 miles southeast of the regional capital of Donetsk, which is controlled by pro-Russian separatists.

In its daily report, the special monitoring mission of the Organization for Security and Cooperation in Europe said a young man had reported that “an unknown armed group” had occupied the grounds of a former children’s campground in the town, Petrivske. According to the report, monitors “spoke to two women, both wearing military uniforms, with caps with Russian Federation Armed Forces insignia.”

“During the conversation with the two women, a vehicle with Russian Federation number plates stopped next to the O.S.C.E. vehicles and two armed men, similarly dressed, exited the car and ordered the women to stop the conversation,” the report stated. Behind a fence surrounding the camp, the monitors “observed one infantry fighting vehicle,” according to the report. The monitors could not enter the camp.