AMMAN/BEIRUT, Dec 7 (Reuters) – Syrian rebels battled government forces for control of the key city of Homs on Saturday and advanced towards the capital Damascus as front lines collapsed across the country, throwing President Bashar al-Assad’s 24-year rule into the balance.

Since the rebels’ sweep into Aleppo a week ago, government defences have crumbled at dizzying speed as insurgents seized a string of major cities and rose up in places where the rebellion had long seemed over.

The twin threats to strategically vital Homs and the capital Damascus now pose an existential threat to Assad’s decades of rule in Syria and the continued influence there of his main regional backer Iran.

A Homs resident, and army and rebel sources said the insurgents had breached government defences from the north and east of the city. A rebel commander said they had taken control of an army camp and villages outside the city.