At least 20 people were killed in clashes Sunday in Syria's Daraa province a day after an explosion killed a group of children, a rights monitor said.
Daraa was the cradle of the 2011 uprising against President Bashar al-Assad but it returned to government control in 2018 under a ceasefire deal backed by Russia.
The southern province has since been plagued by unrest.
The Syrian Observatory for Human Rights monitor said Ahmed al-Labbad, who "leads an armed group", was accused by a rival group of planting an explosive device that killed eight children Saturday in the city of Sanamayn.
Labbad, who previously worked for a state security agency, denied involvement, according to the Britain-based monitor.
On Sunday, a rival armed group led by an individual who previously belonged to ISIS and is now "affiliated with military intelligence", entered Sanamayn and clashes erupted, the monitor said, AFP reported.
The attackers burned the homes of the Labbad family and killed people living there, it added.
Among the 20 dead were three members of Labbad's family and 14 of his fighters, the observatory said.
Syrian state media did not immediately report the clashes.
The official SANA news agency quoted police as saying seven children died in Saturday's explosion in the town, which it blamed on "terrorists".
Attacks, armed clashes and assassinations, some claimed by ISIS, regularly occur in Daraa.
In January, the observatory said a local leader and seven members of an ISIS-affiliated militia were killed in clashes with local groups.
More than 500,000 people have died in Syria's civil war since it erupted in 2011. Millions have been displaced.
