At least 17 people were killed in southern Syria's Daraa province on Sunday in violence triggered by an explosion a day earlier that killed a group of children, local media reports said.
Earlier reports said 12 people had died.
Daraa was the cradle of the 2011 uprising against President Bashar al-Assad's rule but it returned to regime control in 2018 under a ceasefire deal backed by Russia.
The province has since been plagued by dire living conditions and security chaos, with killings and clashes a frequent occurrence.
The Syrian Observatory for Human Rights war monitor said an individual identified as Ahmed al-Labbad, who "leads an armed group", has been accused by rivals of planting an explosive device that went off on Saturday in the province's Sanamayn, killing eight children.
Labbad, who previously worked for a state security agency, has denied planting the device, according to the Britain-based monitor, which relies on a network of sources inside Syria.
On Sunday, a rival armed group led by an individual who "previously belonged to the Islamic State (IS) group and now works for military intelligence" stormed part of Sanamayn and began clashing with Labbad's group, the monitor said.
Labbad's house was torched and "a woman and two children" from his family and seven members of his group were killed, as well as a member of the rival group and an unidentified civilian who was hit by a stray bullet, the Observatory said.
It added that drugs were found at the house and that clashes were ongoing.
Syrian state media did not immediately report Sunday's violence.
State news agency SANA, citing a police source, had provided a different toll for Saturday's blast, saying seven children were killed in the explosion, which it blamed on "terrorists".
متابعة لخبر الاشتباكات في مدينة الصنمين بين مجموعة يقودها "محسن الهيمد" التابع لفرع الأمن العسكري ومجموعة يقودها "أحمد جمال اللباد، الشبط" التابع لفرع أمن الدولة، وتسبب ذلك بمقتل 17 شخصاً، بينهم مدنيون وأطفال، وفقاً للنعوات المنشورة عبر صفحات محلية في مدينة الصنمين، وهم:
1- علاء… pic.twitter.com/AHTnQsyVxc
— Daraa 24 - 24 درعا (@Daraa24_24)
Syria's 13-year war, which erupted after the regime violently repressed peaceful pro-democracy protests, is believed to have killed much more than half a million people and ravaged the country's economy and infrastructure.
Attacks, some claimed by IS, regularly occur in Daraa province, as well as armed clashes and assassinations of government supporters, former opposition figures and civilians working for the government.
Former rebels there who accepted the 2018 Russian-sponsored deal were able to keep their light weapons.
In January, the Observatory said a local leader and seven other members of an Islamist militia affiliated with IS were killed in clashes with local factions in the province.
