Pope Francis has taken a new series of swipes at Russia for its actions in Ukraine, saying its troops were brutal, cruel and ferocious, while praising "brave" Ukrainians for fighting for survival.

But in the text of a conversation he had last month with editors of Jesuit media and published on Tuesday, he also said the situation was not black and white and that the war was "perhaps in some way provoked".

While condemning "the ferocity, the cruelty of Russian troops, we must not forget the real problems if we want them to be solved," Francis said, including the armaments industry among the factors that provide incentives for war. 

"It is also true that the Russians thought it would all be over in a week. But they miscalculated. They encountered  a brave people, a people who are struggling to survive and who have a history of struggle," he said in the transcript of the conversation, published by the Jesuit journal Civilta Cattolica.

"This is what moves us: to see such heroism. I would really like to emphasize this point, the heroism of the Ukrainian people. What is before our eyes is a situation of world war, global interests, arms sales and geopolitical appropriation, which is martyring a heroic people," he said.

Francis said that several months before President Vladimir Putin sent his forces into Ukraine, the pontiff had met with a head of state who expressed concern that NATO was "barking at the gates of Russia" in a way that could lead to war.

Francis then said in his own words: "We do not see the whole drama unfolding behind this war, which was perhaps somehow either provoked or not prevented".

Asking himself rhetorically if that made him "pro-Putin," he said: "No, I am not. It would be simplistic and wrong to say such a thing".

Russia calls its actions in Ukraine a "special operation" to disarm Ukraine and protect it from fascists, a characterisation previously criticised by Francis. Ukraine and the West say the fascist allegation is baseless and that the war is an unprovoked act of aggression.

In his comments, Francis also noted Russia's "monstrous" use of Chechen and Syrian mercenaries in Ukraine.

Francis said he hoped to meet Russian Orthodox Patriarch Kirill at an inter-religious event in Kazakhstan in September. The two had been due to meet in Jerusalem on June but that trip was cancelled because of the war.

Kirill, who is close to Putin, has given the war in Ukraine his full-throated backing. Francis said last month that Kirill could not become "Putin's altar boy", prompting a protest from the Russian Orthodox Church.

In the conversation with the Jesuits, Francis said he had told Kirill during a video call in March: "Brother, we are not clerics of the state, we are pastors of the people".