“Attempts to identify Russian passport holders among them [monitors] are absolutely disgusting. Such things must be nipped in the bud,” he said.
The OSCE monitors are overseeing the implementation of the ceasefire agreement and pullout of heavy artillery in eastern Ukraine in accordance with the peace deal reached by the conflicting sides to the Ukraine crisis in Minsk in February.
According to UN estimates, more than 6,000 people have been killed in Ukraine's east since an armed conflict between Kiev and the self-proclaimed republics of Luhansk in Donetsk erupted in April 2014.
The OSCE Special Monitoring Mission was first deployed to all regions of Ukraine in March 2014. The mission's mandate was extended until March 2016 last month while the number of approved monitors was increased from 500 to 1,000.