Pope Francis has said that he was involved in a prisoner swap between Russia and Ukraine.

Speaking to Jesuits during his trip to Kazakhstan earlier this month, the pope said a Ukrainian military chief and President Volodymyr Zelenskyy’s religious adviser came to him with a request for help.

“This time they brought me a list of more than 300 prisoners. They asked me to do something to make an exchange,” Pope Francis said, according to a transcript published by the Jesuit periodical La Civiltà Cattolica on September 29.

“I immediately called the Russian ambassador to see if something could be done, if an exchange of prisoners could be speeded up.”

The pope did not specify when these conversations about a prisoner swap occurred. He spoke about the exchange in a private conversation with 19 Jesuits in Nur Sultan on Sept. 15 — six days before Zelenskyy announced that Ukraine and Russia had conducted a prisoner swap involving nearly 300 people.

Zelenskyy said that the exchange had been under preparation for a long time. The U.N. Secretary-General António Guterres specifically thanked Turkey and Saudi Arabia for their roles in facilitating the prisoner swap, which involved the return of 215 Ukrainians and 55 Russians and pro-Moscow Ukrainians. It was the largest prisoner exchange since the war began.

In his meeting with the Jesuits, Pope Francis also recalled how he attempted to call Russian President Vladimir Putin after the invasion of Ukraine.

He said: “I recall that the day after the start of the war I went to the Russian Embassy. It was an unusual gesture; the pope never goes to an embassy. He receives the ambassadors personally only when they present their credentials, and then at the end of their mission on a farewell visit. I told the ambassador that I would like to speak with President Putin, provided he left me a small window for dialogue.”

The pope underlined, “from the first day of the war until yesterday, I spoke constantly about this conflict, referring to the suffering of Ukraine.” He later added that in his public statements, he has called “the invasion of Ukraine an unacceptable, repugnant, senseless, barbaric, sacrilegious aggression.”

Pope Francis also said that he believes “international factors contributed to provoking the war.”