Negotiators have lost contact with a group of nuns kidnapped from a Syrian town last year after their captors moved them, a source told AFP on Thursday.
The 13 nuns and three maids were kidnapped from the famed Christian hamlet of Maalula last year and transported to the nearby town of Yabrud, a rebel stronghold the army is fighting to recapture.
"I was in regular contact with them, but since yesterday we've lost contact," a source involved in negotiations said.
"It is very likely that they have been transferred to the region between Yabrud and the Lebanese border" nearby, the source said.
"Contacts are underway to try to ensure their safety."
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The source said the kidnappers were from a group belonging to the Al-Qaeda affiliate Al-Nusra Front led by a man called Abu Malek al-Kuwaiti.
She said they had presented negotiators with a list of demands including the release of all women held in government prisons and the withdrawal of regime forces from Christian religious sites.
The kidnappers also asked for the provision of food to residents of rebel-held areas in the region and "military demands to do with the battle of Yabrud," the source.
"Things that are difficult to achieve," the source added.
The nuns, from both Syria and Lebanon, were kidnapped from a convent in Maalula in December, as regime and rebel forces battled for control in the surrounding Qalamun region.
They were moved to Yabrud, a rebel stronghold that has become the last opposition holdout in the Qalamun region and now at the centre of fierce regime campaign.