Continued from page 1

But the West is wary of such groups, and U.S. officials have said the Obama administration is preparing to designate the Jabhat al-Nusra group, which has alleged ties to al Qaeda, as a terrorist group.

The Observatory said the rebels seized key sectors of the base, home to the 111th Regiment, including its command center.

About 140 Syrian troops fled to a nearby base as the rebels advanced, Mr. Abdul-Rahman said, adding that opposition fighters captured seven government troops and killed two soldiers in the fighting.