Negotiations were reportedly under way for the release of the Orthodox Syrian Archbishop of Aleppo, Mar Gregorios Yohanna Ibrahim, who disappeared nearly six years ago.
The Lebanese newspaper 'al-Akhbar' reported Germany-based Syrian Orthodox priest Samuel Gümüs as saying that the archbishop is being held prisoner by Islamic State militia besieged in the Baghuz area of eastern Syria - the last remaining pocket of territory controlled by the jihadists.
However, the Lebanese newspaper cautions that it is hard to ascertain the accuracy of the information.
Fr Samuel refers to "negotiations currently conducted by the democratic forces of Syria and by the forces of the Allied coalition" in order to also favour the release of Mar Gregorios.
Mar Gregorios Yohanna Ibrahim disappeared on 22 April, 2013 along with Greek Orthodox Metropolitan of Aleppo Boulos al-Yazigi – who is not mentioned in the report - in the area between the Syrian metropolis and the border with Turkey. Since then, no group involved in the Syrian conflict has officially claimed the kidnapping of the two Metropolitan Bishops.
There are unconfirmed rumours that Italian Jesuit Father Paolo Dall'Oglio, abducted that same year, is also being held.
Last month The Times reported the extremist Islamist group was using Dall'Oglio and two other Western hostages, British journalist John Cantlie and a nurse from New Zealand, as "bargaining chips" in negotiations with the US-backed Kurdish-Arab forces surrounding them.
Fr Paolo was kidnapped in Raqqa on 29 July, 2013.