Russia's representative to the Organization for Security and Co-operation in Europe blamed Ukraine's government Friday for the renewed violence in the region that began on Jan. 13.

Speaking at a meeting of the organization's permanent council in Vienna, Andrei Kelin admitted that there had been incidents of violence from "both sides," but nonetheless put the most blame on authorities in Kiev for allegedly provoking the situation.   

"We have warned partners that we clearly see danger signs of the Ukrainian security services' concentration and so-called volunteer battalions near the Donbas. In addition to this, there have been plans for a new wave of military mobilization in Ukraine, to be followed by two more waves in the coming months," Kelin said, according the Russian foreign ministry's website.

Kelin also blamed the Ukrainian side for the deteriorating humanitarian situation in the separatist-controlled areas.

"Ukrainian authorities continue to strengthen the blockade of Donbas and seem to be deliberately worsening the situation of the population living there. Humanitarian aid, deliveries of food, and medicine have been blocked, and social benefits terminated."

In reference to Tuesday's artillery strike on a civilian bus near Volnovakha, which left 12 dead and 18 wounded, Kelin said that "all attacks on civilians" should be strongly condemned, and called for an "objective investigation into the tragedy." 

Kelin concluded his speech by urging a return to the ceasefire regime, which had gone into effect in early December 2014.

"It is extremely important to stop the escalation of tensions. Of key importance is the strict observance of the ceasefire. The use of heavy weapons against residential areas and vital infrastructure, which are clearly provocative, is unacceptable. We urge the Ukrainian authorities to ensure full control over the ceasefire by all units of the armed forces and other units taking part in the military operation."

The conflict between Ukrainian government forces and pro-Russian separatists in eastern Ukraine's Donbas region has claimed over 4,800 lives since it began in April 2014.