"Syrian authorities arrested the wives of three men wanted in the Hama clashes, after they were not able to find (the suspects)," the Arab Organisation for Human Rights (AOHR) said in a statement on Monday.
Two of the women are pregnant and the third has a four-month-old child, the group said.
"The detention of these women is a violation of human rights and violates the Syrian constitution which authorises only the arrest of those responsible for a crime and in accordance with an arrest warrant," AOHR said.
Their husbands are said to be wanted in connection with a firefight that broke out between radicals and security forces on 2 September in the village of Jibril, 210km north of Damascus.
Five men from the group Jund al-Sham (Organisation of the Soldiers of the Levant) were killed in the shootout.
The group only surfaced in March when an internet statement was posted in its name claiming responsibility for a bombing at a theatre in Qatar that killed a Briton.
In late August, security sources said four policemen were killed northeast of Damascus during clashes with fighters from the group.
Jund al-Sham also claimed the October bombings in the Egyptian Red Sea resort of Taba which killed 34 people, most of them Israeli tourists, and an oil refinery explosion in Texas that left 15 people dead.
The authenticity of the group's claims could not be verified.