AMMAN/BEIRUT (Reuters) - Syrian government forces backed by Iranian troops edged closer to a major rebel-controlled highway south of Aleppo on Tuesday, pushing further into insurgent-held areas supported by heavy Russian air strikes.
After seizing a series of villages including Zitan, Humaira and Qalaajiya, the army said it had thrust to the outskirts of Zirba and encircled the town of Khan Touman, an advance rebels said had left them outgunned from the air and ground.
The aim of government forces appeared to be to cut the main Aleppo-Damascus highway that fighters use to transport supplies from rebel-held Idlib province to the north.
Two months of Russian air strikes twinned with army ground offensives backed by Iranian and Lebanese Hezbollah forces have shored up Syrian President Bashar al-Assad in his western heartland. The government side has made gains in Latakia province near Turkey's border, and in southern Aleppo, but they have not tipped the war decisively Assad's way.
Still, a retaking of Khan Touman and attaining the highway would mark the biggest milestone in the offensive in southern Aleppo province where the army and supporting units of Iran's Revolutionary Guard Corps, Hezbollah fighters and Iraqi Shi'ite Muslim militia have already secured large swathes of territory.
Khan Touman housed a large military ammunition store before being seized by rebels in 2013. Retaking it would allow government forces to disrupt rebel lines linking their Aleppo province strongholds with Idlib.
Rebels said the military pressure on them had intensified in the area, and conceded that Khan Touman, 10 km (6 miles) southwest of Aleppo city, could fall back into government hands.
"The situation is bad in general. It is the same story - there is no military balance or even the slightest degree of it," an official in one of the rebel groups operating in the area told Reuters.
"There are planes, artillery, rocket launchers of every type, and militias from all countries," said the official from the Sham Revolutionary Brigades, giving his name as Abu Mohamed.
The government's Aleppo offensive targets a large area to the south of the city near the highway to the capital Damascus in the south. Continued advances would eventually bring the army and its allies to two besieged Shi'ite towns, Kefraya and al-Foua, further to the west.
"We have built fortifications to thwart any new advance," said Yousef al-Issa, a field commander for Ahrar al-Sham, one of the main insurgent groups fighting in the area. "We are trying to disperse their forces but the Russian bombing is holding us back."
Government forces also seek to regain the rebel-held Zirba power plant in the area that once fed parts of Aleppo city. Losing it to rebels, officials say, worsened power shortages in the city of more than three million people, pre-war Syria's commercial capital, officials say.
Last month the army and allied fighters, backed by Russian air strikes, recaptured the town of al-Hader and the Talaat al-Eiss highlands, a move that secured control of most of southern Aleppo countryside.
But reinforcements to the mainly Islamist rebels, including Syria's al Qaeda offshoot Nusra Front, later slowed further government gains.
Reporting by Tom Perry in Beirut and Suleiman Al-Khalidi in Amman; Editing by Mark Heinrich