Tehran has been a staunch ally of Syrian President Bashar al-Assad during the civil war that broke out in 2011. Iran maintains it does not have combat troops in Syria, only officers who provide military advice and training.

Iran-backed Hezbollah, of Lebanon, has for years fought on the side of the Syrian government.

"I am going to Damascus to convey the message of the Islamic Republic to the Syrian government," Araghchi said, emphasising Tehran will "firmly support the Syrian government and army," the IRNA state news agency reported.

Islamist-led rebels on Saturday seized Aleppo's airport and dozens of nearby towns after overrunning most of Syria's second city Aleppo, a war monitor said.

Syria's army confirmed that the rebels had entered "large parts" of the city of around two million people and said "dozens of men from our armed forces were killed".

Araghchi again called the surprise rebel offensive a plot by the United States and Israel.

"The Syrian army will once again win over these terrorist groups as in the past," the foreign minister added.

An Iranian news agency reported earlier that a general in Iran's Islamic Revolutionary Guard Corps was killed in Syria on Thursday during the fighting.

On Saturday, Iran's foreign ministry said its consulate in Aleppo had come under attack, but staff members were safe.

Foreign ministry spokesman Esmaeil Baghaei said Araghchi who will visit Ankara for consultations with Turkish officials after his stop in Damascus.

Since 2020, the rebel enclave in Syria's northwestern Idlib region has been subject to a Turkish- and Russian-brokered truce that had largely been holding despite repeated violations.

But the insurgents' launch on Wednesday of a surprise offensive against the city of Aleppo shattered the truce, the same day a fragile ceasefire took effect in neighbouring Lebanon between Israel and Hezbollah.

The Syrian government had regained control of a large part of the country in 2015 with the support of its Russian and Iranian allies, and in 2016 the entire city of Aleppo.