The death toll in today's suicide bombings at a pair of mosques in the Yemeni capital has risen to 137, with at least 13 children among the dead. A purported affiliate of the Islamic State group claimed responsibility for the bombings, which also wounded 357 people—raising the alarming possibility the extremist group has expanded its presence to Yemen after already setting up a branch in Libya. Earlier this week, the group claimed responsibility for a bloody attack on Western tourists in Tunisia that authorities said was carried out by militants trained in Libya. If the claim is true—and the US expressed skepticism— today's attacks would be the first by the Islamic State group in Yemen.
Shiite rebels known as Houthis have taken over the capital, Sanaa, and nine of the country's 21 provinces over the past six months, raising fears of a civil war tinged with sectarianism. The government of the internationally backed president, Abed Rabbo Mansour Hadi, has fled to the southern port city of Aden. If today's bombings were carried out by Islamic State group supporters, it could be intended as a signal to al-Qaeda, the group's rival—effectively a challenge over turf. That raises the possibility of intra-jihadi fighting as the two compete for recruits by showing who can unleash the worst bloodshed. In its claim of responsibility, an alleged Islamic State affiliate calling itself "Sanaa Province" warned of an "upcoming flood" of attacks targeting the Houthi rebels. (Read more ISIS stories.)