Deportations of Ukrainian children have been a concern since Russia invaded Ukraine last year. Francis said the Holy See had already helped mediate some prisoner exchanges and would do “all that is humanly possible” to reunite families.

“All human gestures help. Gestures of cruelty don’t help,” Francis said.

The International Criminal Court in March issued an arrest warrant for Russian President Vladimir Putin and Russia’s children’s commissioner, accusing them of war crimes for abducting children from Ukraine. Russia has denied any wrongdoing, contending the children were moved for their safety.

Last week Ukrainian Prime Minister Denys Shmyhal met with Francis at the Vatican and asked him to help return Ukrainian children taken following the Russian invasion.

“I asked His Holiness to help us return home Ukrainians, Ukrainian children who are detained, arrested, and criminally deported to Russia,″ Shmyhal told the Foreign Press Association after the audience.

Francis recalled that the Holy See had facilitated some prisoner exchanges, working through embassies, and was open to Ukraine’s request to reunite Ukrainian children with their families.

The prisoner exchanges “went well. I think it could go well also for this. It’s important,” he said of the family reunifications. “The Holy See is available to do it because it’s the right thing,” he added. “We have to do all that is humanly possible.