VIENNA, Sept 9 (Reuters) - A group formed to foster ties between the Roman Catholic and Orthodox churches appealed on Monday for the release of two prominent Syrian bishops still missing after their abduction in Aleppo province in April.
The Syriac Orthodox and Greek Orthodox Archbishops of Aleppo, Yohanna Ibrahim and Paul Yazigi, are the most senior Christian leaders caught up in the revolt against President Bashar al-Assad in which many prominent Muslim clerics have died.
Authorities have blamed the abduction on a "terrorist group", the label they usually give to anti-Assad rebels, but opposition fighters in the northern province denied they kidnapped the two and said they were working for their release.
A declaration from the Vienna-based Pro Oriente foundation called for the immediate release of the clergymen and all others kidnapped in Syria. It sought a negotiated end to the conflict there without any "illegal external military intervention".
Christians make up less than 10 percent of Syria's 23 million people and, like other religious minorities, many have been wary of the mainly Sunni Muslim uprising against Assad, whose Alawite sect is an offshoot of Shi'ite Islam.
The statement on behalf of Austrian Cardinal Christoph Schoenborn and six other church leaders called Christians in the Middle East "an essential and indispensable element of society" who would contribute to building up a society characterised by peace and mutual respect.
Signatories included officials of the Antiochan Orthodox, Syriac Orthodox, Melkite Greek Catholic, Chaldean Catholic, Assyrian and Armenian Catholic faiths, it said.
The two missing bishops had warned of the threat to religious tolerance and diversity from the conflict in Syria, which has killed more than 100,000 of their compatriots.
The fate of Italian Jesuit priest Father Paolo Dall'Oglio, who disappeared in July in eastern Syria, is also still unclear. (Reporting by Michael Shields; Editing by Alison Williams)