Pope Francis Has Asked Russia Three Times to Open a Humanitarian Corridor from Mariupol, But Putin Has Refused 

However, All three times, Putin has refused or given no security guarantees. 

This was reported by the Italian newspaper Il Messaggero with the reference to its sources.

The first two times, Francis asked Putin to open humanitarian route from Mariupol for evacuation of civilians to the Ukraine-controlled territories. These requests were submitted to Putin in the late March and shortly before the Easter through internal confidential channels.    
Pope Francis was even ready to send Konrad Krajewski, the Polish Cardinal, who headed the Office of Papal Charities, to Mariupol after delivery of another ambulance to Ukraine on Pope Francis' behalf.

Finally, Pope asked to allow the ship with a Vatican flag to evacuate civilians trapped in Mariupol's Azovstal, probably because the marine route was the simplest way to reach the besieged steel mill.

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