The bomb exploded outside the town of Salmiyah, killing mostly women and children, the reports said. The Syrian state news agency SANA said the attack left dozens wounded and had caused “very significant” property damage.
The Syrian Observatory for Human Rights, a British-based pro-opposition watchdog group, said the casualty toll was likely to increase.
Salmiyah is known for its Ismaili majority. Ismailism is an offshoot of Shiite Islam, related to the Alawite sect of President Bashar Assad, who has fought a three-year battle against a Sunni-dominated armed opposition. The sectarian civil war has left more than 100,000 people dead.
Separately, activists reported the opening of a new front in fighting between rebel factions in Homs province, a central region previously thought to have been devoid of the presence of the Al Qaeda-affiliated Islamic State of Iraq and Syria, or ISIS. Fighters from the faction abandoned most of their territory in the north, near Aleppo, Idlib and Raqaa, after a six-day rout at the hands of other Islamist groups.
Omar Hariri, a media activist with the Shaam News Network reached via Skype, said clashes between ISIS fighters and brigades of the Free Syrian Army were occurring near Rustun in the northern Homs countryside. Another activist, Abu Yusef, corroborated the reports.
Bulos is a special correspondent.