The Syrian Observatory for Human Rights said the civilians were taken on Thursday in the town of Al-Qaryatain, which IS militants had captured late on Wednesday.
"Daesh kidnapped at least 230 people, including at least 60 Christians, during a sweep through Al-Qaryatain," Observatory chief Rami Abdel Rahman said, using another name for IS.
Bishop Matta al-Khoury, secretary at the Syriac Orthodox Patriarchate in Damascus, told AFP he could not confirm what had happened in the town "because it's very hard to reach residents now".
"But we know that when IS entered the town, it forced some people into house arrest... to use them as human shields" against regime air strikes, Al-Khoury said.
According to Abdel Rahman, many of the Christians had fled from the northern province of Aleppo to seek refuge in Al-Qaryatain.
He said those abducted were wanted by IS for "collaborating with the regime," and their names were on a list used by the extremists as they swept through the town.
Families who tried to flee or hide were tracked down and taken by the extremists, he said. Al-Khoury urged IS to allow residents who want to leave the town to depart.
Al-Qaryatain lies at the crossroads between IS territory in the eastern countryside of Homs and areas further west in the Qalamun area.
It had a pre-war population of 18,000, including Sunni Muslims and around 2,000 Syriac Catholics and Orthodox Christians. Al-Khoury said only 180 Christians were in the town when IS seized it.
In May, masked men abducted Syrian priest Jacques Mourad from the Syriac Catholic Mar Elian monastery in Al-Qaryatain, near the IS-captured ancient city of Palmyra.
Mourad, who was known to help both Christians and Muslims, was preparing aid for an influx of refugees from Palmyra.
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