Syrian government forces have withdrawn from the city of Aleppo following an offensive by rebels opposed to the rule of President Bashar al-Assad.

The army acknowledged that rebels had entered “large parts” of the city, the country’s second largest, but vowed to stage a counterattack.

The offensive marks the most significant fighting in Syria’s civil war in recent years.

More than 300 people, including at least 20 civilians, have been killed since it began on Wednesday, according to the UK-based Syrian Observatory for Human Rights (SOHR).

Speaking on Saturday, President Assad vowed that to “defend [Syria’s] stability and territorial integrity in the face of all terrorists and their backers”.

“[The country] is capable, with the help of its allies and friends, of defeating and eliminating them, no matter how intense their terrorist attacks are,” his office quoted him as saying.

The civil war, which has left around half a million people dead, began in 2011 after the Assad government responded to pro-democracy protests with a brutal crackdown.

The conflict has been largely dormant since a ceasefire agreed in 2020, but opposition forces have maintained control of the north-western city of Idlib and much of the surrounding province.

Idlib sits just 55km (34 miles) from Aleppo, which itself was a rebel stronghold until it fell to government forces in 2016.

The latest offensive has been led by a jihadist group known at Hayat Tahrir al-Sham (HTS) and allied factions backed by Turkey.

HTS was regarded as one of the most effective and deadly of the groups fighting the Assad government and was already the dominant force in Idlib.

The rebels have taken control of Aleppo’s airport and dozens of nearby towns, according to the SOHR.

They also announced a curfew which came into force at 17:00 local time (14:00 GMT) and will remain in place until Sunday.

The Syrian army said rebels had launched “a broad attack from multiple axes on the Aleppo and Idlib fronts” and that battles had taken place “over a strip exceeding 100km (60 miles)”.

Dozens of its soldiers have been killed, it said.

The Russian air force, which played a significant role in keeping Assad in power during the peak of the civil war, carried out air strikes in Aleppo on Saturday.

The strikes marked the first it has staged in the city since helping Syrian government forces recapture it in 2016.

Pictures showed the roads leading out of Aleppo jammed with cars on Saturday as people tried to leave.