The Pope expressed his continuing concern for the abducted "brother bishops, priests and religious, (both) Catholic and Orthodox" at the end of the final Mass of the Year of Mercy's jubilee for teenagers April 24.

"May the merciful God touch the hearts of the kidnappers and grant that our brothers and sisters will be freed as soon as possible and allowed to return to their communities," he said.

"For this reason, I invite you all to pray, without forgetting other people abducted in the world," he said.

His remarks came shortly after the third anniversary of the abductions of Syriac Orthodox Metropolitan Gregorios Yohanna and Greek Orthodox Metropolitan Paul, both of Aleppo, who were kidnapped April 22, 2013, in northern Syria.

The two Orthodox prelates were on a humanitarian mission to secure the release of two priests -- an Armenian Catholic and a Greek Orthodox -- kidnapped earlier that year.

Christians in Syria and war-torn areas of the Middle East and Africa are frequently targeted for kidnappings and acts of violence by terrorist organizations, such as the Islamic State and the Nusra Front.

While some are either murdered or never heard from again, the release of several religious continue to maintain hope that others may still be alive.

Indian Jesuit Father Alexis Prem Kumar, director of Jesuit Refugee Service in Afghanistan, was kidnapped in June 2014 outside a JRS-run school in Herat. He was released by the Taliban after eight months in captivity. However, the fate of others, like Italian Jesuit Father Paolo Dall'Oglio who was kidnapped in Syria in 2013, remain unknown.

More recently, Salesian Father Tom Uzhunnalil was kidnapped in early March from the Missionaries of Charity home in Aden, Yemen, after terrorists entered the facility and murdered four of the sisters and 12 others.

Before leading the faithful in praying the "Regina Coeli" for those missing, Pope Francis called on Christians to entrust "our aspirations and our hopes to the intercession of Mary, the mother of mercy."