Syrian troops have captured a contested suburb of Damascus as the government forged ahead with a offensive that already has taken four other opposition strongholds south of the capital.

For more than a year, much of the belt of neighbourhoods and towns just south of Damascus has been a rebel bastion and a key arms conduit for the opposition.

But government forces – reportedly bolstered by fighters from Lebanon's Shia armed group Hezbollah group and Shia fighters from Iraq - have made significant headway in recent weeks in the area as President Bashar al-Assad pushes to shore up his hold on the capital and its doorstep.

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The town of Hejeira on Wednesday became the latest rebel-held suburb to fall into government hands. The SANA state news agency said the army seized control of the town, but was still battling rebels on the outskirts.

The UK-based Syrian Observatory for Human Rights group confirmed that government forces were in control of most of Hejeira, but said there were still small pockets of resistance.

The opposition's hold on Hejeira became untenable after the military captured the adjacent town of Sabina in recent days.

While the government has driven the rebels from several of their footholds around the capital, the opposition is still within striking distance of the centre of Damascus, and fires barrages of mortar rounds into the city daily.

On Wednesday, mortar shells slammed into the Bab Touma and Zablatani neighborhoods of Damascus, killing at least two people and wounding some 20 others, according to SANA.

In addition to its advances on the periphery of Damascus, the government also has made inroads in recent weeks outside the northern city of Aleppo.

Assad's forces have wrested back a military base near the city's international airport as well as two towns along the highway southeast of the air field.

Aleppo has been a major battlefield since last summer when rebels launched an offensive on the city.

More than a year later, Aleppo is now carved up into rebel- and government-held areas, and fighting has left much of the city in ruins.

'Reoccupying Aleppo'

While the battle for the city has been stalemated for months, the rebels are clearly concerned about the government's latest push.

A group of six prominent rebel brigades has called for all fighters in the city to come together to repel the military offensive, activists say.

The joint declaration said government forces - backed by Shia Hezbollah fighters, Iranian Revolutionary Guards and the Iraqi Abu al-Fadl Abbas armed group - had launched "a fierce offensive to reoccupy" Aleppo.

The fighting in Syria has become increasingly sectarian, with mainly Sunni rebels fighting against loyalists of Assad, who belongs to the Alawite sect, an offshoot of Shia Islam.

The armed opposition in Aleppo and the surrounding countryside has been crippled by recent infighting, which has undermined the rebels in their efforts to remove Assad.

After 32 months of the conflict, which started after Assad's forces fired on anti-regime demonstrators and escalated into a full-blown civil war, the fighting has settled into a stalemate in which scores of people are killed every day.

More than 120,000 people have been killed, according to the UN and opposition activists, and more than two million people have fled to neighbouring countries.

Source: Al Jazeera and agencies