The Syrian army said on Saturday dozens of its soldiers had been killed in a major attack led by Islamist Hayat Tahrir al-Sham rebels who swept into the city of Aleppo, forcing the army to redeploy in the biggest challenge to President Bashar al-Assad in years.

Over a few days, rebel fighters in northern Syria have launched incursions into several major cities with little resistance from government troops.

The Hayat Tahrir al-Sham rebel group in Syria has taken control of much of Aleppo city after local forces withdrew to organize a counteroffensive to retake Aleppo.

Rebel forces in Syria have seized control of most of the city Aleppo after launching a surprise offensive against government forces, a war monitor reported on Saturday as Russia says it deployed fighter jets against rebels in Syria.

The lightning assault on Aleppo by the Islamist militant group Hayat Tahrir al-Sham abruptly redrew the front lines of Syria’s civil war.

Russian and Syrian warplanes targeted insurgents in an Aleppo city suburb on Saturday, two Syrian military sources said, after the rebel fighters penetrated the heart of the city in Syria's northwest in a surprise attack the previous day.

The Hayat Tahrir al-Sham rebel group in Syria has taken control of much of Aleppo city after local forces withdrew to organize a counteroffensive to retake Aleppo.

Video posted by pro-opposition media in Syria shows militants in Aleppo’s western suburbs removing the Syrian national flag from a monument.

Syria state media say government troops are battling insurgents inside the country’s largest city Aleppo for the first time since 2016