The Syrian military rushed reinforcements to the northwest and launched airstrikes Sunday in an attempt to push back insurgents who seized the country's largest city of Aleppo, as Iran pledged to help the government counter the surprise offensive.

Iran has been a key political and military ally of Syrian President Bashar Assad in his country's civil war, but it was unclear how Tehran would support Damascus in the latest flareup. Insurgents led by jihadi group Hayat Tahrir al-Sham launched a two-pronged attack on Aleppo and the countryside around Idlib on Wednesday, before moving toward neighboring Hama province.