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

AMMAN (Reuters) -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 surprise attack, led by the Islamist group Hayat Tahrir al-Sham, was the boldest rebel assault for years in the civil war that has been frozen.

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 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.

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

Russia has carried out air strikes on parts of the Syrian city of Aleppo after areas were seized by rebels opposed to the rule of President Bashar al-Assad. Recent days have seen the most significant offensive against the Syrian government in years and the withdrawal of its military from Aleppo, the country's second largest city.

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

The insurgent offensive, shocking for its speed, has posed the most serious challenge to President Bashar al-Assad in years.

A rebel commander said a fall in Iran-backed manpower created an opening this week's assault. Iran's ally Hezbollah has suffered big losses to Israel.