Tehran says Iran’s foreign minister will go to Syria on Sunday before going to Turkey.

The Syrian army said on Saturday dozens of its soldiers had been killed in a major attack by opposition fighters who swept into the city of Aleppo in the northwest, forcing the army to redeploy in the biggest challenge to President Bashar al-Assad in years.

Tehran has been a staunch ally of al-Assad during the civil war that broke out in 2011, sending thousands of fighters to Syria.

Araghchi, in a phone call with his Syrian counterpart on Friday, accused the United States and Israel of being behind the opposition attack.

During a phone call earlier on Saturday, Araghchi and his Russian counterpart Sergei Lavrov voiced support for Syria, Iranian state media reported.

Araghchi told Lavrov in that the attacks were part of an Israeli-US plan to destabilize the region, state media said.