MASNA, Lebanon — Syrian rebels released a group of about a dozen Greek Orthodox nuns who had been held since December, Lebanon’s official news agency reported Monday.

The release of the nuns and their helpers, 16 women in all, is a rare successful prisoner exchange deal between Syrian government authorities and the rebels seeking to overthrow the rule of President Bashar Assad.

The NNA agency reported early Monday that a convoy of 30 vehicles transporting the freed nuns was heading to the town of Jdeidet Yabous on the Syrian-Lebanon border.

Syrian rebels, including members of the al-Qaida-linked Nusra Front, seized the 13 nuns and their three helpers from the Mar Takla convent when fighters overran the Christian village of Maaloula, north of Damascus, in December.

The nuns, who are believed to be mostly Syrian and Lebanese, worked in the convent’s orphanage. Their seizure confirmed the fears of many in Syria’s minority Christian community that they were being targeted by extremists among rebels. Syria’s three-year conflict has become increasingly sectarian.

Syria’s chaotic mix of rebel groups is overwhelmingly Sunni Muslim. The country’s patchwork of minorities, which includes Christians, Shiite Muslims and the Shiite offshoot, the Alawites, have mostly sided with Assad or remained neutral, fearing for their fate should rebels take power.

About 150 female prisoners are to be released in exchange for the nuns’ freedom, said the head of Lebanon’s General Security agency, Gen. Abbas Ibrahim, who oversaw the deal.