DAMASCUS, Syria - Pope Francis called for prayers Wednesday for 12 Orthodox nuns reportedly taken by force from their convent in Syria by rebels. Religious officials in the region have said the women were abducted, but a Syrian opposition activist said they were merely removed for their own safety.

The 12 nuns join two bishops and a priest who are already believed to be held by hard-line rebels, deepening concerns that extremists in the opposition's ranks are targeting Christians. Syria's minorities, including Christians, have largely sided with President Bashar al-Assad's government or have tried to stay on the sidelines of the country's civil war, fearing for their fate if the rebels, increasingly dominated by Islamic extremists, come to power.

Speaking to a crowd gathered for the pontiff's general audience in St. Peter's Square at the Vatican, Francis invited "everyone to pray for the sisters of the Greek Orthodox monastery of Santa Takla in Maaloula, Syria, who were taken by force by armed men two days ago."

"Let us continue to pray and to work together for peace," he said.

His appeal came as fighting raged in several parts of Syria including the northern city of Aleppo, where rebels firing mortar rounds at government-held neighborhoods killed at least 17 people and wounded dozens more, said Rami Abdurrahman of the Britain-based Syrian Observatory for Human Rights.

Activists also reported clashes in the Qalamoun region north of Damascus, an area that controls the smuggling routes from Lebanon that help sustain rebel-held enclaves.

The region boasts a sizable Christian population and is home to the ancient village of Maaloula and its Mar Takla convent.