VATICAN CITY — Pope Francis is calling for the rapid release of two bishops kidnapped by gunmen in Syria while on a humanitarian mission.

Bishop Boulos Yazigi of the Greek Orthodox Church and John Ibrahim of the Assyrian Orthodox Church were abducted as they traveled from the Turkish border to the city of Aleppo on Monday. Their driver was killed. It was not immediately clear who was responsible.

The Pope on Tuesday called the abduction is "a dramatic confirmation of the tragic situation in which the Syrian population and its Christian community is living."

SANA news agency said the two were seized by "a terrorist group" in the village of Kfar Dael as they were "carrying out humanitarian work."

Several prominent Muslim clerics have been killed in Syria's uprising against President Bashar al-Assad, but the two bishops are the most senior church leaders caught up in the conflict which has killed more than 70,000 people across Syria.

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Christians make up less than 10 percent of the country'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 Shiite Islam.

Fears for their future if the rebels were to end 40 years of Assad dynastic rule, which ensured religious freedom without political rights, have increased with the growing strength of Islamist rebels and a pledge of allegiance to al-Qaida by the hardline Nusra Front rebels two weeks ago.

In the past week, government troops have overrun villages near the Lebanese border and suburbs of Damascus, including two districts west of the capital where activists say regime forces killed more than 100 people.