Syrian and Russian jets are stepping up strikes on opposition forces in northern Syria in retaliation for the sudden offensive that has cost the regime control of the country’s second largest city, Aleppo.

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:

The rebels captured much of Aleppo a day earlier in a surprise offensive. They now control a broad patch across the provinces of Hama, Idlib and Aleppo, in the west and northwest of Syria, according to officials from the rebel-linked administration and the war monitor.