The Syrian regime forces and Iran-backed militias escalated attacks on an opposition-held area in Deraa, a possible prelude to a large-scale campaign to wrest full control of the southern city, rebels and residents said on Monday.
The raids and bombings mainly hit the southern part of Deraa, strategically located on the border with Jordan where the Syrian uprising erupted six years ago. Reinforcements from the army and its allies, the Iranian-backed Lebanese group Hezbollah and Shia Muslim Iraqi militias, are being rushed to the city from several locations near Damascus.
"The regime has brought large columns of troops from the elite 4th Armoured Division, and also Hezbollah forces," said Major Issam al Rayes, a spokesman of the Southern Front group of the Free Syrian Army (FSA) rebels.
The Syrian regimes forces recently intensified dropping barrel bombs – drums or cylinders packed with shrapnel – and has fired hundreds of so-called elephant rockets on Deraa's old quarter and a former refugee camp nearby, rebels and residents said.
The reinforcements were using the Damascus-Deraa highway, a major supply route where well-fortified trenches on both sides of the road have made it more difficult for rebels to mount attacks.
The Syrian army has not commented on its troop build-up in Deraa or the escalating aerial bombing.
The regime's strategic goal is to open a direct route from Damascus to the Jordanian border.
"Large-scale military campaign"
The opposition says the troop build-up and relentless aerial bombing in recent weeks pointed to a major campaign for what the FSA rebels see as a decisive battle.
"Everything indicates the regime is preparing for a large-scale military campaign in Deraa in which they plan to encircle the city and reach the Jordanian border," Rayes said.
"Our surveillance shows troop carriers and heavy armour ... if it continues at this same level of reinforcements, this will be very large," said Adham al Karad, the commander of the missile brigade in the FSA's Southern Front.
The army had stepped up its campaign to regain the strategic district of Manshiya neighbourhood that almost completely fell into rebel hands after four months of street battles.
The opposition stormed Manshiya, the last army foothold in Deraa's rebel-held old quarter, in February to ward off any army attempt to capture a strategic crossing with Jordan.
The army's control of the crossing, a once-thriving passenger and commercial gateway with Jordan, would sever the opposition link between the eastern and western parts of the province they control, dealing a major blow to their cause in the south.