The al-Qaeda-linked Hayat Levant Liberation Committee and the Turkey-backed Nour el-Din el-Zinki group blamed each other for triggering Tuesday's fighting in the northern province of Aleppo, AP reported.
Syria media reported that the al-Qaeda-linked militants captured the villages of Taqad, Saadiyah and Habata.
They added that fighting is ongoing in the town of Daret Azzeh.
The Levant Liberation Committee says Nour el-Din el-Zinki militants shot dead five people, including four of its militants, last week.
The clashes are the first between the two former allies since they reached a deal to end similar fighting in October.