In a Friday report, Los Angeles Times cited Samir Zaitoun, a commander with Al Tawheed Brigade, a Syrian opposition group, as saying that nearly half the militants in Aleppo, mostly from small groups, have left over the last year.
"A lot of people left because it's taking so long; they thought it was going to be a matter of yelling 'God is great' twice in protest and a few hits and it would be over," Zaitoun said.
The Syrian army has been making more advances in recent months.
On July 13, the Syrian army recaptured parts of the eastern town of Mulayhah after about 100 days of heavy fighting with militants in the area.
Takfiri terrorists have recently stepped up their attacks against civilians as Syrian army soldiers have achieved major victories in their battle against the foreign-backed militants.
Syria sank into war in March 2011, when pro-reform protests turned into a massive insurgency following the intervention of Western and regional states.
According to reports more than 150,000 people have been killed and millions displaced in the turmoil.
SHI/SHI