Syrian rebels have launched a surprise offensive against Syrian President Bashar al-Assad’s regime, a significant escalation in Syria’s civil war, which is raising concerns about a potential wider regional conflict in the Middle East.

Cities in Syria have been hit by Russian air strikes throughout the weekend, as anti-government rebels have advanced in Aleppo. Hundreds of people have been killed in fighting since Wednesday, when the current offensive began. Here are some key takeaways from our reporting over the past few hours:

NBC News’ Matt Bradley reports on the intensifying violence in the Syrian rebel offensive after Russian and Syrian jets struck a rebel held city in the northern part of the country. Syrian President Bashar Assad is vowed to crush insurgents waging a shock offensive against his regime.