WASHINGTON – The Syrian regime has moved some chemical weapons to safeguard the material as it wages war against rebel forces but the main storage sites for its arsenal remain secure, US Defense Secretary Leon Panetta said Friday. “There has been some intelligence that with regards to some of these sites there has been some movement ...in order for the Syrians to better secure the chemicals,” Panetta told a joint news conference with his Canadian counterpart. “We still believe, based on what we know and what we're monitoring, that the principal sites remain secure,” he said. Asked if rebel forces had gotten their hands on some chemical stockpiles, Panetta said: “I don't have any specific information about the opposition and whether or not they've obtained some of this or how much they've maintained.” Syria's chemical weapons stockpile, which dates back to the 1970s, is the largest in the Middle East, but its precise scope remains unclear, according to analysts. The regime has said it might use its chemical weapons if attacked by outside countries, although not against its own people. Meanwhile, fighting over Syria's largest city intensified Friday, with the most widespread battles reported there in two months as rebel forces launched a new offensive to rout President Bashar Al-Assad's forces from Aleppo, activists said. Some of the heaviest fighting erupted in the predominantly Kurdish neighborhood of Sheikh Maksoud, which was drawn into the conflict for the first time. Kurds make up Syria's largest minority and have been split in their loyalties. Since the uprising against Assad began 18 months ago, some Kurds have sided with the rebels while others have supported the regime. Aleppo's Sheikh Maksoud neighborhood is mostly under the control of a pro-government Kurdish group. There were conflicting reports on whether Kurdish gunmen took part in Friday's fighting. Aleppo, a city of 3 million that was once a bastion of support for Assad, has emerged as a key battleground in Syria's civil war. Its fall would give the opposition a major strategic victory, with a stronghold in the north near the Turkish border. A rebel defeat, at the very least, would buy the regime more time. “The city is witnessing one of the most violent days. All fronts are on fire,” Aleppo-based activist Baraa Al-Halabi said. A mortar round fired during fighting Friday in the area of a Syrian-Turkish border crossing, Tel Abyad, landed in Turkish territory, damaging the walls of two houses in the town of Akcakale, its mayor, Abdulhakim Ayhan, told the state-run Anadolu Agency. No one was hurt. Anadolu said Assad's forces were firing mortar rounds on rebel positions in a bid to regain control of the border crossing. Also, a Syrian activist group, the Local Coordination Committees, said a Syrian warplane bombed the northern town of Azaz near the Turkish border, killing seven people. An amateur video showed at least one dead boy being removed from under the rubble of a house in the area. – Agencies