Syrian insurgents have reached the suburbs of Damascus as part of a rapidly moving offensive that has seen them take over some of Syria’s largest cities, opposition activists and a rebel commander said Saturday.

Rami Abdurrahman, who heads the Britain-based Syrian Observatory for Human Rights, an opposition war monitor, said insurgents are now active in the Damascus suburbs of Maadamiyah, Jaramana and Daraya. He added that opposition fighters on Saturday were also marching from eastern Syria toward the Damascus suburb of Harasta.

A commander with the insurgents, Hassan Abdul-Ghani, posted on the Telegram messaging app that opposition forces have started carrying out the “final stage” of their offensive by encircling Damascus. He added that insurgents were headed from southern Syria toward Damascus.

The Syrian army withdrew from much of southern Syria, leaving more areas of the country, including two provincial capitals, under the control of opposition fighters, the military and an opposition war monitor said.

The redeployment away from the provinces of Daraa and Sweida came as Syria’s military sent large numbers of reinforcements to defend the key central city of Homs, Syria’s third largest, as insurgents approached its outskirts.

The rapid advances by insurgents is a stunning reversal of fortunes for Syria's President Bashar Assad, who appears to be largely on his own, with erstwhile allies preoccupied with other conflicts.

His chief international backer, Russia, is busy with its war in Ukraine, and Lebanon's powerful Hezbollah, which at one point sent thousands of fighters to shore up his forces, has been weakened by a yearlong conflict with Israel. Iran, meanwhile, has seen its proxies across the region degraded by Israeli regular airstrikes.

Rami Abdurrahman, who heads the Syrian Observatory for Human Rights, a Syria war monitor, reported Saturday that Iran’s military advisers have started leaving Syria. He added that Iran-backed fighters in eastern Syria, mainly from Afghanistan and Pakistan, have withdrawn into central Syria. AP