AMMAN/BEIRUT - President Bashar al-Assad's artillery pounded rebel-held areas around Aleppo on Friday, preparing the ground for an onslaught on Syria's biggest city where the United States has said it fears a "massacre" may be imminent. Opposition sources said the shelling, which follows intensive ground and air bombardment of the city itself, was an attempt to stop fighters from resupplying rebel units inside Aleppo. "They are shelling at random to instil a state of terror," said Anwar Abu Ahed, a rebel commander outside the city. The battle for Aleppo, a major power centre that is home to 2.5 million people, is being seen as a potentially game changing turning point in the 16-month uprising against Assad that could give one side an edge in a conflict where both the rebels and the government have struggled to gain the upper hand. A rebel commander said insurgents had attacked a convoy of Syrian army tanks heading towards the city, as the government continued to redeploy forces from other parts of the country to bolster its forces there. The fate of Syria itself - an ethnically fragmented nation of 22 million people - is likely to determine the future of the wider region for years to come amid fears that its own sectarian tensions could spill across its porous borders. The US State Department said credible reports of tank columns moving on Aleppo, along with air strikes by helicopters and fixed-wing aircraft, represented a serious escalation of Assad's efforts to crush his opponents. "This is the concern: that we will see a massacre in Aleppo, and that's what the regime appears to be lining up for," Victoria Nuland, a spokeswoman for the State Department, said. As the remaining residents of Aleppo braced themselves for more bloodshed, General Robert Mood, the outgoing head of the UN monitoring mission, told Reuters he thought Assad's days in power were numbered. "In my opinion it is only a matter of time before a regime that is using such heavy military power and disproportional violence against the civilian population is going to fall," the Norwegian general, who left Damascus on July 19, said. Navay Pillay, the United Nations human rights chief, said a pattern had emerged as Assad's forces resorted to shelling, tank fire and door-to-door searches. "All this, taken along with the reported build-up of forces in and around Aleppo, bodes ill for the people of that city," Pillay said in statement. Government troops stationed on the outskirts of the city unleashed barrages of heavy-calibre mortar rounds on its western neighbourhoods, while Russian-built MI-25 helicopter gunships struck in the east, opposition activists in the city said. The heavy fighting follows an audacious bomb attack that killed four of Assad's closest lieutenants in Damascus on July 18, a development that led some analysts to speculate that the government's grip was slipping.
