Pope Francis has written to the U.N. secretary-general appealing for "action to end the humanitarian tragedy now underway" against Christians and other religious minorities in Iraq.

In the letter released Wednesday, Francis urged U.N. agencies "responsible for security, peace, humanitarian law and assistance to refugees" to aid the plight of religious minorities forced to flee from their homes.

The letter, dated. Aug 9, said "the violent attacks that are sweeping across Northern Iraq cannot but awaken the consciences of all men and women of goodwill to concrete acts of solidarity."

Francis has stepped up his denunciation of the attacks against Christians and religious minorities in Iraq. He has also sent a personal envoy, Cardinal Fernando Filoni, to the region to show solidarity with the victims.