Instead, blaming the upsurge in violence on the Ukrainians and the rise in civilian deaths on “those who issue such criminal orders,” as he did on Friday in Moscow, Mr. Putin is apparently doubling down, rather than backing down, in a conflict that is now the bloodiest in Europe since the Balkan wars.

With the appearance in recent weeks of what NATO calls sophisticated Russian weapons systems, newly emboldened separatist leaders have abandoned all talk of a cease-fire. One of the top leaders of the Russian-backed rebels said Friday that his soldiers were “on the offensive” in several sectors, capitalizing on their capture of the Donetsk airport the day before.

“We will attack” until the Ukrainian Army is driven from the border of the Donetsk region, Aleksandr Zakharchenko, leader of the Donetsk People’s Republic rebel group, said in comments carried by Russian news agencies.

“On our side, we won’t make an effort to talk about a cease-fire,” Mr. Zakharchenko said. “Now we’re going to watch how Kiev reacts. Kiev doesn’t understand that we can attack in three directions at once.”