A car bomb stuck a religious procession in a Shia rebel bastion of north Yemen on Wednesday, killing 15 people and rattling a fragile truce with the government, a rebel spokesman and a tribal chief said.
"Seventeen people were killed and 15 wounded in the car bombing that targeted a Shia procession in Al-Jawf province," rebel spokesman Mohammed Abdulsalam told AFP by telephone.
Abdulsalam said the attack targeted the faithful who were preparing to mark Al-Ghadeer, the day on which Shia commemorate the annointment of Ali, one of the key figures of their faith, as successor to the Prophet Mohammed.
The anniversary has long been a source of contention between the Sunni and Shia branches of the faith and a tribal leader in the province told AFP that the bombing was the work of a Sunni militant loyal to Al Qaeda.
"A suicide bomber driving a four-wheel drive vehicle blew himself up alongside the procession," the tribal chief said. "Among the dead was provincial tribal chief Hussein bin Ahmed bin Hadhban and his son," he added.
Other tribal sources warned that the death toll was likely to rise. One told AFP it "could reach 30."
Yemen is the ancestral homeland of Al Qaeda leader Osama Bin Laden and has been a growing focus for the operations of his worldwide jihadist network sparking a sharp increase in US military aid.
The mountains in the west of Al-Jawf province and neighbouring Saada have been a stronghold of Zaidi Shia rebels in the uprising they have been waging against the Sanaa government on and off for the past six years.
The office of the UN High Commissioner for Refugees (UNHCR) warned on Tuesday that there had been an "alarming escalation" in fighting in the region, despite a truce signed between the rebels and Sanaa in February.
The agency said that aid agencies and witnesses had reported that clashes between the rebels and pro-government tribes had erupted in Saada province on November 13.
"At least 20 people have been killed reportedly and others wounded over the past 10 days in the worst violence in northern Yemen since the signing of the ceasefire in February," UNHCR spokesman Andrej Mahecic said, speaking before the latest unrest.