Syrian army units aided by pro-Iranian militias have staged a major assault on an opposition enclave in the southern border city of Deraa in a bid to retake the last opposition stronghold in southern Syria, residents, army and opposition sources said.

Troops amassed around the sprawling government-held city sought to advance into the area known as Deraa al Balaad, which has particular significance in the Syrian conflict as it was the center of the first peaceful protests against the Assad family rule in 2011 which were met by deadly force before spreading across the country.

Opposition fighters said they had repulsed the attack from the western side of the enclave, which has been under a two-month siege during which the army has prevented food, medical and fuel supplies coming in but opened a corridor for civilians to leave, residents and local figures said.

The Syrian army, aided by Russian airpower and Iranian militias, in 2018 retook control of the province of which Deraa is the capital and which borders Jordan and Israel's Golan Heights.