On Sunday, the head of the OSCE mission claimed independence fighters had barred monitors from entering Debaltsevo, the city where several thousand Kiev troops remain encircled by militia.
Igor Plotnitsky told RIA Novosti that he met a team of monitors Monday when he visited areas in the vicinity of the frontline in eastern Ukraine.
"Yesterday I saw their vehicles near Alchevsk, some 15 kilometers from the frontline. No one told me anything. I did not talk to them, no one talked to me or made any statements," he said.
OSCE monitors have been deployed in southeastern Ukraine since March 2014 after an escalation of tensions between Kiev forces and independence supporters. They are closely watching the situation in the conflict regions and publish daily reports.
The OSCE monitors have repeatedly reported being denied access to some of the war-torn areas. The mission demanded unrestricted and safe access to all areas of eastern Ukraine, saying that it is necessary to ensure a strict implementation of the ceasefire, which came into force Sunday.