Syrian rebels said they seized an important military airport and an air defense base just outside Damascus on Sunday, adding to a monthlong string of tactical successes -- capturing bases, disrupting supply routes and seizing weaponry -- that demonstrate their ability to erode the government's dominance despite facing withering aerial attacks.

In the past month, rebels have seized or damaged major military bases around the country, making off with armored vehicles, antiaircraft weapons and other equipment they desperately need to break the stalemate in the grinding conflict, which has taken more than 30,000 lives. But they have not tried to hold all of the bases, as they become easy targets for government airstrikes.

The capture of the air base near Damascus, Marj al-Sultan, was one of the principal bases used by the Syrian Air Force to resupply army units and to carry out bomb and rocket attacks.