Fierce fighting raged in key Syrian cities on Tuesday ahead of the UN General Assembly meeting, as international peace envoy Lakhdar Brahimi said he saw no end in sight to the brutal 18-month old conflict. Global Aid agency \"Save the Children\" said that Syrian children are being \"badly traumatised\" after witnessing killings, torture and other atrocities, a day after at least 12 children were among 116 people reported killed nationwide. Powerful explosions also rocked a military building in Damascus, causing casualties, the Syrian Observatory for Human Rights reported. \"The explosions were so powerful that the walls collapsed,\" Observatory director Rami Abdel Rahman told AFP of the headquarters on the Damascus airport road of the administration that manages schools for the children of martyred soldiers. Regime forces again bombarded Aleppo in the north, focusing on the Hanano and Maysar districts in the east and Kalassa in the southwest, the Britain-based Observatory said. It also said soldiers shot dead a young girl when they targeted the car she was in after midnight on the motorway linking the northern commercial hub to Damascus. On Monday Brahimi, the UN and Arab League envoy, painted a grim picture of the Syrian crisis. \"There is no prospect for today or tomorrow to move forward,\" he told reporters after briefing the UN Security Council on his talks in mid-September with President Bashar al-Assad. Reporting on his first visit to Syria since assuming his post, Brahimi said Assad \"knows something must change,\" but he wants only a return to \"the old Syria\" which he and his father have ruled for more than 40 years. Brahimi talked of food shortages, the \"mediaeval\" torture of detainees, and damage to all but 200 of the country\'s 2,200 schools. The veteran troubleshooter, who took over from former UN secretary general Kofi Annan as Syria envoy on September 1, also appealed to the divided 15-nation Security Council for united backing for his efforts. The conflict has divided the Security Council, where Russia and China have already wielded their veto powers three times to resist international action demanded by Western and many Arab states. Syria was set to be spotlighted again later on Tuesday when US President Barack Obama is expected to lead Western demands for action on the conflict, when the annual UN General Assembly begins. Obama will be one of the opening speakers at the gathering of world leaders where Syria, mounting fears of a military strike on Iran and anti-West protests in Muslim nations are set to dominate. UN chief Ban Ki-moon, France\'s President Francois Hollande and Qatar\'s emir, Sheikh Hamad bin Khalifa al-Thani, a key backer of the Syrian opposition, are also expected to lambast Assad on the opening morning. Ahead of the General Assembly, Egypt\'s President Mohamed Morsi told the US television channel PBS that he opposes any foreign military intervention in Syria but believes Assad must go. Since mid-July, the conflict has centred on Aleppo, where Free Syrian Army rebels say they control all of the axes around the northern metropolis, and that their only real worry is attack from the air. The FSA said one of its commanders, regime defector Colonel Kassem Saadeddine who is also a rebel spokesman, escaped an assassination attempt early on Tuesday. \"Colonel Saadeddine\'s convoy was ambushed by shabiha (pro-regime militiamen) after midnight in Salmiyeh in Hama province\" in central Syria, spokesman Fahd al-Masri told AFP. \"A large battle ensued and the shabihas were killed. The colonel was saved.\" Saadeddine commands rebels in the central province of Homs and is also the official FSA spokesman inside Syria. AFP reporters say troops loyal to Damascus have been forced to retreat on many fronts in the northern regions of Aleppo and Idlib, where rebels have captured hundreds of square kilometres (miles) of territory. \"The army is unable to control the ground, so it tries to stay in power by dominating the skies,\" Abdel Rahman told AFP. On Monday, an air strike killed five people, including three children from the same family, in Aleppo. The Observatory said at least 2,000 children have been killed in Syria over the past 18 months. \"Children should be going back to school, but instead they are suffering extreme violence,\" Abdel Rahman said. \"This would not be possible were the international community not silenced by its paralysis.\" Save the Children said it has collected \"shocking testimony\" that \"children have been the targets of brutal attacks, seen the deaths of parents, siblings and other children, and have witnessed and experienced torture.\" Released on Tuesday, \"Untold Atrocities\" is a collection of first-hand accounts of the conflict from Syrian children and parents after fleeing the country, and contains graphic details of how children have been caught up in the war. At least 29,000 people have been killed since the revolt erupted last year, according to the Observatory, while the United Nations puts the toll at more than 20,000. The Daily Star