A helicopter hovers above al-Bab Aleppo -- a warning sign of what's to come.<br/> <br />The Syrian army bombarded the rebel-held town for a second day in a row. Rights groups say at least 20 people were killed on Sunday, after the government dropped improvised barrel bombs on a market district. It came a day after 26 were killed in a similar attack on the same town by President Bashar al-Assad's forces.<br/> <br />Barrel bombs - are typically rolled out of the back of helicopters and are rarely delivered with any accuracy.<br/> <br />The video which can not be independently verified shows the carcasses of destroyed buildings.<br/> <br />Syria's state news agency said the army had destroyed "several terrorist dens" including the headquarters of one Islamist group.<br/> <br />Rebel forces are fighting to the finish. The bombardment of Al-Bab, just north east of Aleppo city follows gains by Assad's forces in south-east Aleppo last month and could herald a similar ground offensive in the area.<br/> <br />There's l
