* Western-backed rebels say they are not responsible for abduction
* Archbishops are the most senior church figures caught up in war
* Church says no contact with kidnappers
By Oliver Holmes
BEIRUT, April 23 (Reuters) - Western-backed Syrian rebels in the province of Aleppo denied on Tuesday that they had kidnapped two prominent Syrian archbishops but said they were working for their release and trying to find out who had taken them.
Colonel Abdel-Jabbar Oqaidi, head of the rebel military council in Aleppo, said in a statement that his group was "ready to negotiate with any entity, even if it is the regime (of President Bashar al-Assad), for their release".
The archbishops are the most senior church figures seemingly caught up in the fight between Assad's forces and rebels trying to end four decades of Assad family rule.
The conflict has killed more than 70,000 and sent a wave of fear across minority groups as rebels led by the Sunni Muslim majority gain ground in northern Syria. Many rebel units are joining Islamist groups, including the Nusra Front, which has allied itself to al Qaeda.
As Assad's forces have retreated from many parts of Aleppo, other groups have moved in and created fiefdoms, including Kurdish militias and Islamists who distance themselves from Oqaidi's group, the military wing of the Western-backed Syrian National Coalition.
Razek Siriani, a representative of the Syriac Orthodox Archdiocese of Aleppo, said that Greek Orthodox archbishop Paul Yazigi and Syriac Orthodox archbishop Yohanna Ibrahim had been seized on their way to the Turkish border after a humanitarian mission to help release two priests kidnapped months earlier.
He said that details of the kidnapping were unclear - the Syrian government said on Monday that the bishops had been travelling to, not from, Aleppo - but that the driver had been shot dead and a fourth member of the group managed to escape.
Siriani said the church did not know who was holding the bishops but that the fourth member of the group had reported that the kidnappers had foreign accents and light faces, and might be Chechens.
Greece said it had activated its Foreign Ministry's crisis management mechanism.
The two bishops' churches - the Greek Orthodox and Syriac Orthodox Churches "of Antioch and All the East" - are both based in Damascus, with followers across the Middle East, part of a worldwide family of Orthodox churches.
The Greek Orthodox Church of Antioch in Damascus declined to comment on the kidnappings.
The Syrian government blames opposition groups and the bishops were abducted in a rebel-held area. Armed gangs who kidnap for ransom are setting up in Syria in increasing numbers. There are also an undetermined number of foreign Muslim fighters, including Chechens, who have come to Syria for "jihad" or holy war and are helping the rebels fight Assad's forces. (Additional reporting by Renee Maltezou and Harry Papachristou in Athens and Tom Heneghan in Paris; Editing by Kevin Liffey)