NATO Secretary-General Anders Fogh Rasmussen has said he was "extremely concerned" about the escalation of tensions in eastern Ukraine.
In a statement on April 13, Rasmussen denounced a “concerted campaign of violence by pro-Russian separatists, aiming to destabilize Ukraine as a sovereign state."
Drawing parallels with Ukraine’s Crimea region, which Russia annexed last month after deploying forces there, Rasmussen added: "The reappearance of men with specialized Russian weapons and identical uniforms without insignia, as previously worn by Russian troops during Russia's illegal and illegitimate seizure of Crimea, is a grave development.”
Rasmussen called on Russia to "de-escalate" the situation and to pull back its troops from the area around Ukraine's border.
"Any further Russian military interference, under any pretext, will only deepen Russia's international isolation," he added.
Based on reporting by AFP and Reuters