The Syrian Observatory for Human Rights (SOHR) monitoring group said Saturday that Islamist groups now control most of the city of Aleppo, AFP reported.

The terrorists have launched a lightning offensive against Syrian government forces backed by Iran and Russia since Wednesday, the same day a fragile truce between Israel and Lebanon's Hezbollah movement, an ally of Damascus, took effect in neighboring Lebanon after two months of all-out warfare.

“ Hayat Tahrir al-Sham and allied groups ... have taken control of most of the city, government centers and prisons,” SOHR said.

The Islamist alliance, led by the former Syrian branch of al-Qaeda, controls much of the Idlib region in northwestern Syria, as well as parts of the neighboring provinces of Aleppo, Hama and Latakia.

Overnight, Russian warplanes raided areas of Aleppo city for the first time since 2016, added the organization, which relies on a network of sources inside Syria.

The death toll rose to 311 in days of clashes - 183 from the Islamist group and allied groups backed by Turkey, 100 soldiers and pro-government forces, and 28 civilians.

State media said four civilians were killed when shelling hit a student dormitory in Aleppo.

An AFP correspondent reports how Islamists were celebrating the capture of Aleppo on Friday night. Another correspondent saw Islamist fighters in front of the city's main landmark, the Citadel.

SOHR, for its part, reported that “Aleppo's governor and police and security commanders have withdrawn from the city center.”

The overnight airstrikes coincided with “the arrival of large military reinforcements in the area,” SOHR reported.

Army reinforcements have arrived in Aleppo, a Syrian security official told AFP on Friday, while an army statement said troops had repelled an attack on the city and recaptured some positions.

SOHR director Rami Abdel Rahman told AFP on Saturday that the Islamists quickly seized most of Aleppo without encountering significant resistance.

“There was no fighting, not a single shot was fired as the regime forces retreated,” he said.

The organization said the Islamists and their allies made other gains in the north, including capturing the strategically important town of Saraqib, located on the road to Aleppo about 40 kilometers to the southwest.

The Russian military said on Friday it was bombing extremist forces, while Turkey demanded an end to bombardment of the Idlib region.

Earlier, it was reported that pro-Turkish Islamist groups fighting Bashar al-Assad's government forces launched a surprise offensive in northwestern Syria.

The Islamists are led by the radical group Hayat Tahrir al-Sham, which broke away from al-Qaeda in 2017.