Syrian rebels have reportedly breached the city of Aleppo itself, according to open source analysts and the Syrian Observatory for Human Rights, as thousands of insurgent fighters make startling advances in their surprise offensive against President Bashar al-Assad's regime in northwestern Syria. Videos circulating online appear to show rebels in the outskirts of Aleppo, Syria's second largest city. The rebels launched a major offensive three days ago and since then have moved swiftly towards Aleppo, capturing swathes of countryside and villages. The offensive reignites the frontline in Syria for the first time in years and the Assad regime and its allies Russia and Hezbollah appear to be struggling to hold it back.