BEIRUT - A powerful blast ripped through a pickup truck in the southern province of Daraa in Syria early Wednesday, killing 21 people including four children, a monitoring group said.
"Twenty-one people were killed in the Nawa area (of Daraa), among them four children and six women, in a blast that detonated as their vehicle went past Tal al-Jumua," said the Syrian Observatory for Human Rights.
A battalion of troops loyal to Syrian President Bashar al-Assad "is positioned there, and is under siege by rebel forces. Activists blamed regime troops for planting the explosives", said the Britain-based group.
Daraa is the cradle of the uprising that broke out against Assad in March 2011.
More than 115,000 people have been killed in the war that broke out after Assad's troops unleashed a brutal crackdown against protesters calling for political change.
Rebels fighting Assad's troops have made significant progress in recent months in Daraa, which is strategically located on the border with Jordan and near Damascus province.
In the northeastern province of Hasake fierce clashes pitting Kurdish fighters against jihadists resumed, killing at least 10 Al-Qaeda fighters, the Observatory said.
Clashes have raged in majority Kurdish areas for months, as the jihadist Islamic State of Iraq and the Levant (ISIL) has sought to expel the Committees for the Protection of the Kurdish People (YPG) from areas under their control.
Wednesday's clashes hit the Kharrab Bajar area, and resulted in the killing of at least 10 ISIL fighters and the YPG's takeover of an Islamist checkpoint, said the Observatory.
Analysts say ISIL aims to crush competition from other armed groups active in areas out of the control of Assad's regime, and that its war with the Kurds is part of the strategy for control of territory and resources.
Elsewhere, Assad's loyalists pressed a campaign designed to crush rebels positioned near the capital, as fresh clashes broke out on the edges of rebel-held Douma east of Damascus, said the Observatory.