"I urge Russia to withdraw all its forces from eastern Ukraine, to stop all its support for the separatists and to respect the Minsk agreement," NATO Secretary General Jens Stoltenberg said in the Latvian capital Riga, Censor.NET reports citing i24News.
"The cease-fire has not been respected," he told reporters before meeting with EU defense ministers, and said he was "deeply concerned by the deteriorating situation" in eastern Ukraine.
"Russian forces, artillery and air defense units, as well as command and control elements are still active in Ukraine," he said, adding that "there has been a steady buildup of tanks and armored vehicles across the border from Russia to Ukraine."
"The refusal of the separatists to respect the cease-fire threatens the agreement, as does the denial of access to the area for OSCE monitors."
Stoltenberg urged Moscow to "use all its influence on the separatists to make them respect the cease-fire".
"We will provide practical support for Ukraine, with modernizing and reforming the defense army and of course we are also adapting our own defense posture to the fact that we see that the security environment in Europe is changing because of the actions of Russia in Ukraine."
Earlier, Stoltenberg stated that the separatists used advanced weapons to attack the Ukrainian forces in Debaltseve.