Syria\'s rebels accused strongman Bashar al-Assad on Tuesday of moving chemical weapons to the country\'s borders, a day after his beleaguered regime said it would use its stockpiles if attacked. Helicopter gunships strafed rebel neighbourhoods of second city Aleppo, as heavy fighting forced the closure of a third of the shopping malls of what is Syria\'s commercial capital, pro-government media said. The rebel Free Syrian Army said the regime\'s chemical arsenal had been moved in a bid to pressure the international community, much of which has called for Assad to step aside in the face of the more than 16-month uprising against his rule. \"According to our information, the regime began moving its stocks of weapons of mass destruction several months ago... with the goal of putting pressure on the region and the international community,\" a statement said. At a Damascus news conference on Monday, foreign ministry spokesman Jihad Makdissi acknowledged that Syria has chemical weapons and said the regime would use them if attacked by outsiders, although not against its own civilians. \"Syria will not use any chemical or other unconventional weapons against its civilians, and will only use them in case of external aggression,\" Makdissi said. \"Any stocks of chemical weapons that may exist, will never, ever be used against the Syrian people,\" he said, adding that in the event of foreign attack, \"the generals will be deciding when and how we use them.\" US President Barack Obama warned Assad not to make the \"tragic mistake\" of unleashing chemical weapons. \"Given the regime\'s stockpile of chemical weapons, we will continue to make it clear to Assad and those around him that the world is watching,\" Obama told an audience of US veterans in the western state of Nevada. \"They will be held accountable by the international community and the United States should they make the tragic mistake of using those weapons,\" he added. Analysts said they doubted whether in the current conflict Assad\'s regime would resort to using a chemical weapons stockpile that was developed as a counterbalance to Israel\'s presumed nuclear arsenal. \"It\'s not at all in the interest of the Syrian army to use these weapons -- there is no tactical interest given the nature of the current conflict which is mainly urban,\" said Olivier Lepick, specialist in chemical weaponry at the Foundation for Strategic Research in Paris. \"The regime knows that if it did so it would lose the support of China and Russia.\" As rebel fighters suffered setbacks, notably in Damascus, the opposition Syrian National Council bickered over whether it would accept a transition led temporarily by a member of the regime if Assad steps aside. An offer to do so by SNC spokesman George Sabra was contradicted just hours later by SNC spokeswoman Bassma Kodmani. \"There was never any question of a national unity government led by a member of the regime,\" Kodmani told AFP. Despite the disarray in opposition ranks, Turkish Prime Minister Recep Tayyip Erdogan, whose country hosts the rebel leadership, said he was confident it was close to victory. \"The ruthless killings committed in panic in recent days show the world that the Syrian regime is on the road to oblivion,\" he said. Neighbouring Iran warned it would not tolerate the collapse of its key regional ally. \"The Syrian people and the friends of Syria will not allow regime change,\" Brigadier General Masoud Jazayeri, the deputy chief of Iran\'s joint armed forces, was quoted as saying. Activists and regime sources say government forces have reclaimed most of Damascus after a week of heavy fighting with rebels, who remain in the city but are planning a guerrilla strategy. Clashes continued Tuesday, with the Britain-based Syrian Observatory for Human Rights reporting at least 33 people killed nationwide. \"At least seven civilians, including six children, were killed by regime forces shelling of the besieged town of Herak,\" south of Damascus, the watchdog said. A video it distributed showed the bodies of dead children, including a young girl in a pink and white dress, lying on a blood-smeared floor, the faces of some of them covered in blood. \"Herak has been under shelling for 10 days,\" an unidentified man says in the amateur video. \"Where are the Arabs and Muslims when these children are killed during Ramadan?\" he pleaded, referring to the Muslim holy month which began last week. In Aleppo, the Observatory said helicopter gunships were firing on the Qadi Askar, Bab Al-Hadid, Al-Katergi and Karam Al-Jabal districts. The Al-Watan newspaper, close to the government, reported that six shopping malls -- a third of the commercial hub\'s total -- had been forced to close because of \"regrettable events\". Riad Kahwaji, director for the Institute for Near East and Gulf Military Analysis, said that as the regime throws its full weight into protecting its control over Damascus, the rebels have made a tactical retreat and are now \"directing their full force on Aleppo.\" \"Taking Aleppo after they take control of the borders of Turkey makes sense because it\'s all connected, close to supply routes, close to the command headquarters of the rebels on the borders,\" he told AFP.