If rebels capture the complex in Allepo, which also houses several smaller army outposts, it would be another setback for the Assad regime. In recent weeks, the regime has lost control of key infrastructure in the northeast including a hydroelectric dam, a major oil field and two army bases along the road linking Aleppo with the airport to its east.
Rebels also have been hitting the heart of Damascus with occasional mortars shells or bombings, posing a stiff challenge to Assad's regime in its seat of power.
On Saturday, opposition fighters in the eastern province of Deir el-Zour overran a site known as al-Kibar, which was home to what is believed to have been a partly built nuclear reactor that Israeli warplanes bombed in 2007.
A year after the strike, the U.N. nuclear watchdog determined that the destroyed building's size and structure fit specifications of a nuclear reactor. Syria never stated the purpose of the site.
After the bombing, the regime carted away all the debris from the destroyed building and equipment from the two standing structures, analysts said, adding that the rebels were unlikely to have found any weapons in the abandoned complex.