Archbishop Mor Gregorius Yohanna Ibrahim and Archbishop Boulos Yazigi were abducted in 2013, and there has been no sign of life from them since then, stated the Society for Threatened Peoples (STP) in Göttingen on Monday.
According to the STP, there are indications that radical Syrian Islamists, who were and are supported by Turkey, were involved in the abduction.
According to Kamal Sido, the STP's expert, the Pope could use his moral authority to press for justice in Turkey. The families and friends of the abducted bishops are still waiting for certainty.
"Turkey can and must use its influence on the actors in Syria to finally clarify the situation," emphasised Sido.
Commitment to minorities and members of the opposition
The Pope could also stand up for the rights of minorities in Turkey. "Kurdish activists and democratic opposition members are still being persecuted. A just peace between Kurds and Turks would be a turning point - also for the lives of Christians and other minorities," said Sido.
The Pope is travelling to Turkey on Thursday morning. The occasion is the 1,700th anniversary of the First Ecumenical Council in Nicaea.
A joint prayer with the Orthodox Patriarch of Constantinople, Bartholomew I, is planned there. Leo is also scheduled to visit the Turkish President Recep Tayyip Erdogan.
The STP is also calling on the head of the church to visit the Tur Abdin region, the historical home of the Syrian Orthodox Christians, during his trip: "A visit to the Mor Gabriel Monastery would be a strong sign of support. This ancient religious heritage has been under pressure for years and needs international attention in order to survive."