At least 25 people were killed in northwestern Syria in air strikes carried out by the Syrian government and Russia, the Syrian opposition-run rescue service known as the White Helmets said early on Monday.

At least 25 civilians, including 10 children and four women, were killed on Sunday in Russian and Syrian government airstrikes on the Syrian city of Idlib and rural Aleppo, the White Helmets announced Monday.

As things stand this morning, the Syrian army says that anti-government forces have now taken control of "large parts" of Aleppo. Meanwhile, the country's president is vowing to "defend [Syria's] stability and territorial integrity in the face of all terrorists and their backers".

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.

Warplanes targeted the city of Idlib in an attempt to fend off advances made by antigovernment forces that included a stunning assault on Aleppo.

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.

Russian and Syrian fighter jets have struck the rebel-held city of Idlib on Dec. 1 amid attempts to push back an insurgency that has taken over most of Aleppo, Reuters reported, citing Syrian army sources.

On Sunday, Russian and Syrian jets stepped up their bombing of northwestern Syria, targeting rebel-held areas, Reuters reports. According to Reuters, on December 1, aircraft from both nations struck the city of Idlib in northern Syria,

Syria and Russia are stepping up their retaliatory strikes on forces in northern Syria after they lost control of the country’s second-largest city.