By Levent Tok, Mohamad Misto, Halit Suleyman

AZAZ, Syria

Syrian army and Iran-backed militias captured Sunday five opposition-held districts in east of Aleppo, Syria’s northwestern province, local sources told Anadolu Agency.

Ahmet Karaali, a spokesman for the Ahrar al-Sham opposition group, said opposition forces withdrew from the districts in east Aleppo after three days of fighting against Iran-backed militias.

Thousands of civilians fled to the interior of the city during the withdrawal, he added.

While noting that clashes were still ongoing in the eastern al-Sahur district, Karaali denied allegations regime forces captured the area.

If regime forces capture al-Sahur, the besieged region of opposition-held areas would be divided into north and south.

The PYD/PKK also carried out attacks in the region, pro-opposition civil defense official Ibrahim Ebu Leys told Anadolu Agency.

More than 508 civilians have been killed and 1,871 others injured since mid-November in regime attacks on Aleppo – once the second largest city in Syria.

In the last 10 days, all hospitals and medical facilities have halted operations because of attacks. School activities have also been disrupted.

Syria has been locked in a devastating civil war since early 2011, when the regime of President Bashar al-Assad cracked down on pro-democracy protests -- which erupted as part of the "Arab Spring" uprisings -- with unexpected ferocity.

Since then, hundreds of thousands of people are believed to have been killed and millions more displaced by the conflict.